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General Information - Summary of Consolidated Subsidiaries (Detail) - KRW (₩)
₩ in Millions
 12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Disclosure of subsidiaries [line items]      
Total assets ₩ 40,989,810 ₩ 37,159,341  
Total liabilities 22,577,114 20,592,180  
Operating revenues 25,638,855 24,898,005 ₩ 24,099,394
Profit (loss) for the year ₩ 1,385,635 ₩ 1,459,395 ₩ 746,256
KT Linkus Co., Ltd [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Linkus Co., Ltd. KT Linkus Co., Ltd KT Linkus Co., Ltd.
Type of Business Public telephone maintenance    
Location Korea    
Controlling percentage ownership 92.40% 92.40%  
Closing month December    
Total assets ₩ 47,734    
Total liabilities 47,498    
Operating revenues 76,135    
Profit (loss) for the year ₩ (614)    
KT Submarine Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Submarine Co., Ltd. KT Submarine Co., Ltd. KT Submarine Co., Ltd.
Type of Business Submarine cable construction and maintenance    
Location Korea    
Controlling percentage ownership 32.90% 39.30%  
Closing month December    
Total assets ₩ 120,255 ₩ 110,390 ₩ 116,813
Total liabilities 7,884 10,736 14,032
Operating revenues 42,848 31,374 110,201
Profit (loss) for the year ₩ (12,126) ₩ (3,183) ₩ 1,197
KT Telecop Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Telecop Co., Ltd. KT Telecop Co., Ltd. KT Telecop Co., Ltd.
Type of Business Security service    
Location Korea    
Controlling percentage ownership 86.80% 86.80%  
Closing month December    
Total assets ₩ 370,004 ₩ 363,224 ₩ 318,456
Total liabilities 230,965 233,797 193,737
Operating revenues 517,406 515,456 392,489
Profit (loss) for the year ₩ 4,267 ₩ 3,985 ₩ 212
KT Alpha Co., Ltd. (KT Hitel Co., Ltd.) [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Alpha Co., Ltd. (KT Hitel Co., Ltd.) KT Alpha Co., Ltd. (KT Hitel Co., Ltd.) KT Alpha Co., Ltd. (KT Hitel Co., Ltd.)
Type of Business Data communication    
Location Korea    
Controlling percentage ownership 73.00% 73.00%  
Closing month December    
Total assets ₩ 406,236 ₩ 390,671 ₩ 288,949
Total liabilities 172,211 172,767 92,599
Operating revenues 516,737 471,870 350,231
Profit (loss) for the year ₩ 13,115 ₩ (8,692) ₩ 2,080
KT Service Bukbu Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Service Bukbu Co., Ltd. KT Service Bukbu Inc. KT Service Bukbu Inc.
Type of Business Opening services of fixed line    
Location Korea    
Controlling percentage ownership 67.30% 67.30%  
Closing month December    
Total assets ₩ 74,673 ₩ 59,341 ₩ 60,825
Total liabilities 65,820 54,070 56,554
Operating revenues 252,304 231,602 217,451
Profit (loss) for the year ₩ 3,227 ₩ 1,128 ₩ (871)
KT Service Nambu Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Service Nambu Co., Ltd. KT Service Nambu Inc. KT Service Nambu Inc.
Type of Business Opening services of fixed line    
Location Korea    
Controlling percentage ownership 77.30% 77.30%  
Closing month December    
Total assets ₩ 80,450 ₩ 62,513 ₩ 58,182
Total liabilities 66,479 52,695 51,460
Operating revenues 301,720 271,174 264,776
Profit (loss) for the year ₩ 3,067 ₩ 1,430 ₩ (456)
KT Commerce Inc. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Commerce Inc.    
Type of Business B2C, B2B service    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KT Strategic Investment Fund No.2 [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Strategic Investment Fund No.2    
Type of Business Investment fund    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KT Strategic Investment Fund No.3 [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Strategic Investment Fund No.3    
Type of Business Investment fund    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KT Strategic Investment Fund No.4 [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Strategic Investment Fund No.4    
Type of Business Investment fund    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KT Strategic Investment Fund No.5 [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Strategic Investment Fund No.5    
Type of Business Investment fund    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
BC-VP Strategic Investment Fund No.1 [member]      
Disclosure of subsidiaries [line items]      
Subsidiary BC-VP Strategic Investment Fund No.1    
Type of Business Investment fund    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
BC Card Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary BC Card Co., Ltd. BC Card Co., Ltd. BC Card Co., Ltd.
Type of Business Credit card business    
Location Korea    
Controlling percentage ownership 69.50% 69.50%  
Closing month December    
Total assets ₩ 5,666,075 ₩ 3,933,427 ₩ 3,084,398
Total liabilities 4,109,200 2,481,004 1,778,751
Operating revenues 3,897,090 3,580,970 3,387,640
Profit (loss) for the year ₩ 148,341 ₩ 120,308 ₩ 39,455
VP Inc. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary VP Inc.    
Type of Business Payment security service for credit card, others    
Location Korea    
Controlling percentage ownership 69.70% 50.90%  
Closing month December    
H&C Network [member]      
Disclosure of subsidiaries [line items]      
Subsidiary H&C Network H&C Network Co., Ltd. H&C Network
Type of Business Call center for financial sectors    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 82,737 ₩ 88,616 ₩ 269,651
Total liabilities 6,640 4,993 61,365
Operating revenues 27,392 227,604 322,690
Profit (loss) for the year ₩ 992 ₩ 11,995 ₩ 2,413
BC Card China Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary BC Card China Co., Ltd.    
Type of Business Software development and data processing    
Location China    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
INITECH Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary INITECH Co., Ltd    
Type of Business Internet banking ASP and security solutions    
Location Korea    
Controlling percentage ownership 61.30% 58.20%  
Closing month December    
Smartro Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Smartro Co., Ltd    
Type of Business VAN (Value Added Network) business    
Location Korea    
Controlling percentage ownership 64.50% 64.50%  
Closing month December    
KTDS Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KTDS Co., Ltd. KTDS Co., Ltd. KTDS Co., Ltd.
Type of Business System integration and maintenance    
Location Korea    
Controlling percentage ownership 95.60% 95.50%  
Closing month December    
Total assets ₩ 401,932 ₩ 341,358 ₩ 183,297
Total liabilities 228,474 199,831 133,129
Operating revenues 723,161 632,899 499,990
Profit (loss) for the year ₩ 30,941 ₩ 21,464 ₩ 10,635
KT M&S Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT M&S Co., Ltd. KT M&S Co., Ltd. KT M&S Co., Ltd.
Type of Business PCS distribution    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 255,310 ₩ 241,377 ₩ 231,260
Total liabilities 204,336 203,051 197,306
Operating revenues 730,802 710,634 661,533
Profit (loss) for the year ₩ 8,105 ₩ 3,496 ₩ (485)
GENIE Music Corporation [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary GENIE Music Corporation   GENIE Music Corporation
Type of Business Online music production and distribution    
Location Korea    
Controlling percentage ownership 36.00% 36.20%  
Closing month December    
Total assets     ₩ 250,538
Total liabilities     88,488
Operating revenues     247,237
Profit (loss) for the year     ₩ 9,472
KT MOS Bukbu Co.,Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT MOS Bukbu Co., Ltd. KT MOS Bukbu Co., Ltd. KT MOS Bukbu Co., Ltd.
Type of Business Telecommunication facility maintenance    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 38,684 ₩ 32,511 ₩ 32,167
Total liabilities 22,553 25,402 26,070
Operating revenues 83,085 70,212 67,975
Profit (loss) for the year ₩ 4,607 ₩ 1,637 ₩ 1,473
KT MOS Nambu Co., Ltd [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT MOS Nambu Co., Ltd. KT MOS Nambu Co., Ltd. KT MOS Nambu Co., Ltd.
Type of Business Telecommunication facility maintenance    
Location Korea    
Controlling percentage ownership 98.40% 98.40%  
Closing month December    
Total assets ₩ 42,011 ₩ 36,741 ₩ 33,765
Total liabilities 25,416 26,053 24,947
Operating revenues 83,330 71,940 71,259
Profit (loss) for the year ₩ 5,035 ₩ 2,016 ₩ 1,639
KT Skylife Co Ltd [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Skylife Co., Ltd. KT Skylife Co., Ltd. KT Skylife Co., Ltd.
Total assets ₩ 1,359,166 ₩ 1,275,645 ₩ 919,476
Total liabilities 503,679 469,694 175,039
Operating revenues 1,038,468 772,950 706,631
Profit (loss) for the year ₩ 20,941 ₩ 62,309 ₩ 58,190
KT Skylife [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Skylife    
Type of Business Satellite TV    
Location Korea    
Controlling percentage ownership 50.20% 50.30%  
Closing month December    
Skylife TV Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Skylife TV Co., Ltd.    
Type of Business TV contents provider    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KT Estate Inc. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Estate Inc. KT Estate Inc. KT Estate Inc.
Type of Business Residential building development and supply    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 2,480,333 ₩ 2,370,940 ₩ 1,689,601
Total liabilities 833,842 791,884 325,429
Operating revenues 478,188 577,578 365,335
Profit (loss) for the year ₩ 58,780 ₩ 213,203 ₩ 14,370
KT Investment Management Inc. (KT AMC Co., Ltd.) [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Investment Management Inc. (KT AMC Co., Ltd.)    
Type of Business Asset management, real estate and consulting services    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
NEXR Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary NEXR Co., Ltd.    
Type of Business Cloud system implementation    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KTGDH Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KTGDH Co., Ltd. KTGDH Co., Ltd.  
Type of Business Data center development and related service    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 12,059 ₩ 11,464  
Total liabilities 1,596 1,560  
Operating revenues 4,323 4,423  
Profit (loss) for the year ₩ 451 ₩ 553  
KT Sat Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Sat Co., Ltd.    
Type of Business Satellite communication business    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 677,980    
Total liabilities 89,644    
Operating revenues 185,313    
Profit (loss) for the year ₩ 28,073    
Nasmedia, Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Nasmedia, Co., Ltd    
Type of Business Solution provider and IPTV advertisement sales business    
Location Korea    
Controlling percentage ownership 44.00% 44.00%  
Closing month December    
KT Sports Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Sports Co., Ltd.    
Type of Business Management of sports teams    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 28,220    
Total liabilities 15,461    
Operating revenues 65,350    
Profit (loss) for the year ₩ (7,302)    
K T Music Contents Fund No.2 [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Music Contents Fund No.2 KT Music Contents Fund No.2 KT Music Contents Fund No.2
Type of Business Music and contents investment business    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 15,718 ₩ 14,985 ₩ 15,021
Total liabilities 277 278 285
Operating revenues 1,040 253 169
Profit (loss) for the year ₩ 735 ₩ (30) ₩ (116)
KT-Michigan global contents fund [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT-Michigan Global Content Fund KT-Michigan Global Contents Fund KT-Michigan Global Contents Fund
Type of Business Content investment business    
Location Korea    
Controlling percentage ownership 88.60% 88.60%  
Closing month December    
Total assets ₩ 2,371 ₩ 3,552 ₩ 10,382
Total liabilities 27 112 175
Operating revenues 33 13,592 111
Profit (loss) for the year ₩ (1,095) ₩ 10,032 ₩ (1,420)
KTCS Corporation [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KTCS Corporation KTCS Corporation KTCS Corporation
Type of Business Database and online information provider    
Location Korea    
Controlling percentage ownership 34.10% 32.20%  
Closing month December    
Total assets ₩ 419,726 ₩ 416,750 ₩ 384,919
Total liabilities 228,618 234,172 215,175
Operating revenues 1,031,010 968,499 933,006
Profit (loss) for the year ₩ 17,634 ₩ 19,034 ₩ 11,323
KTIS Corporation [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KTIS Corporation KTIS Corporation KTIS Corporation
Type of Business Database and online information provider    
Location Korea    
Controlling percentage ownership 33.30% 31.40%  
Closing month December    
Total assets ₩ 396,208 ₩ 369,361 ₩ 294,289
Total liabilities 199,204 177,619 126,894
Operating revenues 536,229 487,801 454,172
Profit (loss) for the year ₩ 15,917 ₩ 24,944 ₩ 7,387
KT M Mobile Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT M Mobile Co., Ltd.    
Type of Business Special category telecommunications operator and sales of communication device    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 152,114    
Total liabilities 49,816    
Operating revenues 262,918    
Profit (loss) for the year ₩ 4,731    
KT Investment Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Investment Co., Ltd. KT Investment Co., Ltd. KT Investment Co., Ltd.
Type of Business Financing business for new technology    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 103,354 ₩ 87,366 ₩ 115,627
Total liabilities 79,182 66,108 93,695
Operating revenues 15,136 21,040 47,801
Profit (loss) for the year ₩ 2,840 ₩ (697) ₩ 4,680
PlayD Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary PlayD Co., Ltd.    
Type of Business Advertising agency    
Location Korea    
Controlling percentage ownership 70.40% 70.40%  
Closing month December    
Next Connect PFV Inc. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary Next Connect PFV Next Connect PFV Inc. Next Connect PFV Inc.
Type of Business Residential building development and supply    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets   ₩ 518,441 ₩ 394,268
Total liabilities   167,963 37,271
Operating revenues   0 26
Profit (loss) for the year   ₩ (6,519) ₩ (7,101)
KT Rwanda Networks Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Rwanda Networks Ltd. KT Rwanda Networks Ltd. KT Rwanda Networks Ltd.
Type of Business Network installation and management    
Location Rwanda    
Controlling percentage ownership 51.00% 51.00%  
Closing month December    
Total assets ₩ 126,721 ₩ 125,860 ₩ 114,768
Total liabilities 267,369 236,389 191,781
Operating revenues 30,834 23,328 17,870
Profit (loss) for the year ₩ (27,467) ₩ (28,770) ₩ (34,610)
AOS Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary AOS Ltd. AOS Ltd. AOS Ltd.
Type of Business System integration and maintenance    
Location Rwanda    
Controlling percentage ownership 51.00% 51.00%  
Closing month December    
Total assets ₩ 10,972 ₩ 11,539 ₩ 11,812
Total liabilities 905 2,812 3,875
Operating revenues 8,049 6,942 5,719
Profit (loss) for the year ₩ 1,274 ₩ 823 ₩ 296
KT Japan Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Japan Co., Ltd. KT Japan Co., Ltd. KT Japan Co., Ltd.
Type of Business Foreign investment business and local counter work    
Location Japan    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 1,888 ₩ 1,474 ₩ 2,694
Total liabilities 3,141 2,633 2,622
Operating revenues 3,263 1,298 1,853
Profit (loss) for the year ₩ 226 ₩ (142) ₩ 1
East Telecom LLC [member]      
Disclosure of subsidiaries [line items]      
Subsidiary East Telecom LLC East Telecom LLC  
Type of Business Wireless/fixed line internet business    
Location Uzbekistan    
Controlling percentage ownership 91.60% 91.60%  
Closing month December    
Total assets ₩ 42,691 ₩ 35,904  
Total liabilities 21,645 22,088  
Operating revenues 27,030 11,960  
Profit (loss) for the year ₩ 6,419 ₩ 2,487  
KT America, Inc. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT America, Inc. KT America, Inc. KT AMERICA, INC
Type of Business Foreign investment business and local counter work    
Location USA    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 5,945 ₩ 4,884 ₩ 4,498
Total liabilities 843 101 125
Operating revenues 8,070 6,508 6,808
Profit (loss) for the year ₩ 37 ₩ 201 ₩ 712
PT BC card Asia Pacific [member]      
Disclosure of subsidiaries [line items]      
Subsidiary PT. BC Card Asia Pacific    
Type of Business Software development and supply    
Location Indonesia    
Controlling percentage ownership 99.90% 99.90%  
Closing month December    
KT Hong Kong Telecommunications Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Hong Kong Telecommunications Co., Ltd. KT Hong Kong Telecommunications Co., Ltd. KT Hong Kong Telecommunications Co., Ltd.
Type of Business Fixed line telecommunication business    
Location Hong Kong    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 10,505 ₩ 6,613 ₩ 6,159
Total liabilities 4,768 1,346 2,800
Operating revenues 20,413 18,825 16,386
Profit (loss) for the year ₩ 51 ₩ 1,313 ₩ 1,308
Korea Telecom Singapore Pte.Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary Korea Telecom Singapore Pte. Ltd.    
Type of Business Foreign investment business and local counter work    
Location Singapore    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Texnoprosistem LLC [member]      
Disclosure of subsidiaries [line items]      
Subsidiary Texnoprosistem LLC    
Type of Business Fixed line internet business    
Location Uzbekistan    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Nasmedia Thailand Co Ltd [member]      
Disclosure of subsidiaries [line items]      
Subsidiary Nasmedia Thailand Co., Ltd.    
Type of Business Internet advertising solution    
Location Thailand    
Controlling percentage ownership 99.90% 99.90%  
Closing month December    
KT Huimangjieum [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Huimangjieum    
Type of Business Manufacturing    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 6,984    
Total liabilities 2,582    
Operating revenues 22,860    
Profit (loss) for the year ₩ 494    
K-REALTY RENTAL HOUSING REIT 3 [member]      
Disclosure of subsidiaries [line items]      
Subsidiary K-REALTY RENTAL HOUSING REIT 3    
Type of Business Residential building    
Location Korea    
Controlling percentage ownership 88.60% 88.60%  
Closing month December    
Storywiz Co Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Storywiz Co., Ltd.   Storywiz Co., Ltd
Type of Business Contents and software development and supply    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets     ₩ 21,594
Total liabilities     10,065
Operating revenues     19,209
Profit (loss) for the year     ₩ (1,954)
KT Engineering Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Engineering Co., Ltd.    
Type of Business Telecommunication facility construction and maintenance    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KT Studio Genie Co Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Studio Genie Co., Ltd. KT Studio Genie Co., Ltd.  
Type of Business Data communication service and data communication construction business    
Location Korea    
Controlling percentage ownership 90.90% 100.00%  
Closing month December    
Total assets ₩ 987,270 ₩ 648,534  
Total liabilities 268,911 276,933  
Operating revenues 723,580 90,047  
Profit (loss) for the year ₩ 189,498 ₩ (16,443)  
KHS Corporation [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KHS Corporation    
Type of Business Operation and maintenance of facilities    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Lolab Co Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Lolab Co., Ltd. Lolab Co., Ltd.  
Type of Business Truck transportation and trucking arrangement business    
Location Korea    
Controlling percentage ownership 79.80% 80.00%  
Closing month December    
Total assets ₩ 35,091 ₩ 26,726  
Total liabilities 17,247 897  
Operating revenues 74,881 2,107  
Profit (loss) for the year ₩ (7,985) ₩ (134)  
HCN Co Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary HCN Co., Ltd.    
Type of Business Cable television service    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Millie Seojae [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Millie Seojae    
Type of Business Book contents service    
Location Korea    
Controlling percentage ownership 38.60% 38.60%  
Closing month December    
KT ES Pte Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT ES Pte. Ltd. KT ES Pte. Ltd.  
Type of Business Foreign investment business    
Location Singapore    
Controlling percentage ownership 57.60% 57.60%  
Closing month December    
Total assets ₩ 240,721 ₩ 240,331  
Total liabilities 88,640 80,597  
Operating revenues 78,815 15,157  
Profit (loss) for the year ₩ (23,957) ₩ (6,355)  
Epsilon Global Communications Pte. Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Epsilon Global Communications PTE. Ltd.    
Type of Business Network service industry    
Location Singapore    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Epsilon Telecommunications US Pte Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Epsilon Telecommunications (US) PTE. Ltd.    
Type of Business Fixed line telecommunication business    
Location Singapore    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Epsilon Telecommunications [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Epsilon Telecommunications (SP) PTE. Ltd.    
Type of Business Fixed line telecommunication business    
Location Singapore    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Epsilon Telecommunications Limited [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Epsilon Telecommunications Limited    
Type of Business Fixed line telecommunication business    
Location UK    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Epsilon Telecommunications HK Limited [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Epsilon Telecommunications (HK) Limited    
Type of Business Fixed line telecommunication business    
Location Hong Kong    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Epsilon US Inc [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Epsilon US Inc.    
Type of Business Fixed line telecommunication business    
Location USA    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Epsilon Telecommunications BG EOOD [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Epsilon Telecommunications (BG) EOOD    
Type of Business Employee support service    
Location Bulgaria    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Epsilon M E A General Trading LLC [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Epsilon M E A General Trading LLC    
Type of Business Local counter work    
Location United Arab Emirates    
Controlling percentage ownership 49.00% 49.00%  
Closing month December    
Nasmedia KT Alpha Future Growth Strategic Investment Fund [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Nasmedia-KT Alpha Future Growth Strategic Investment Fund    
Type of Business Investment fund    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KT Strategic Investment Fund 6 [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Strategic Investment Fund 6    
Type of Business Investment fund    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Alticast Company Limited [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Alticast Company Limited    
Type of Business Software development and delivery    
Location Vietnam    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Altimedia Corporation [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Altimedia Corporation Altimedia Corporation  
Type of Business Software development and delivery    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 44,861 ₩ 32,338  
Total liabilities 15,777 9,742  
Operating revenues 47,203 6,968  
Profit (loss) for the year ₩ 6,035 ₩ 1,037  
Alticast B V [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Alticast B.V.    
Type of Business Software development and delivery    
Location Netherlands    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
BCCARD VIETNAM LTD. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary BCCARD VIETNAM LTD.    
Type of Business Software sales business    
Location Vietnam    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KTP SERVICES INC. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KTP SERVICES INC.    
Type of Business Fixed line telecommunication business    
Location Philippines    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 3,832    
Total liabilities 2,044    
Operating revenues 776    
Profit (loss) for the year ₩ (255)    
KT RUS LLC [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT RUS LLC    
Type of Business Foreign investment business    
Location Russia    
Controlling percentage ownership 100.00%    
Closing month December    
Total assets ₩ 967    
Total liabilities 16    
Operating revenues 5    
Profit (loss) for the year ₩ (871)    
Hangang Real Estate Investment Trust No. 24 [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Hangang Real Estate Investment Trust No. 24    
Type of Business Investment fund    
Location Korea    
Controlling percentage ownership 75.00%    
Closing month December    
kt cloud Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary kt cloud Co., Ltd.    
Type of Business Information telecommunication business    
Location Korea    
Controlling percentage ownership 100.00%    
Closing month December    
Total assets ₩ 1,348,684    
Total liabilities 245,872    
Operating revenues 432,118    
Profit (loss) for the year ₩ 14,712    
KT DX Vietnam Company Limited [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT DX Vietnam Company Limited    
Type of Business Software development    
Location Vietnam    
Controlling percentage ownership 100.00%    
Closing month December    
Total assets ₩ 1,815    
Total liabilities 6    
Operating revenues 0    
Profit (loss) for the year ₩ 26    
Pocheon Jeonggyori Development Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Pocheon Jeonggyori Development Co., Ltd.    
Type of Business Residential building development    
Location Korea    
Controlling percentage ownership 80.90%    
Closing month December    
Alpha DX Solution Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Alpha DX Solution Co., Ltd.    
Type of Business Data communication service    
Location Korea    
Controlling percentage ownership 100.00%    
Closing month December    
PT CRANIUM ROYAL ADITAMA [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary PT CRANIUM ROYAL ADITAMA    
Type of Business Software development    
Location Indonesia    
Controlling percentage ownership 67.00%    
Closing month December    
KT Primorye IDC LLC [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Primorye IDC LLC    
Type of Business Data processing and associated service delivery    
Location Russia    
Controlling percentage ownership 99.00%    
Closing month December    
Juice Inc. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Juice Inc.    
Type of Business Online information provider/Software development and delivery    
Location Korea    
Controlling percentage ownership 41.20%    
Closing month December    
Spark and Associates Inc. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary SPARK AND ASSOCIATES INC.    
Type of Business Network service industry    
Location Korea    
Controlling percentage ownership 100.00%    
Closing month December    
KT Powertel Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KT Powertel Co., Ltd.
Total assets     ₩ 119,694
Total liabilities     18,833
Operating revenues     65,897
Profit (loss) for the year     3,809
KT Linkus Co Ltd [member]      
Disclosure of subsidiaries [line items]      
Total assets   ₩ 54,219 58,372
Total liabilities   53,316 54,022
Operating revenues   81,434 84,519
Profit (loss) for the year   ₩ (3,095) ₩ (3,212)
KT Sports Inc [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KT Sports Inc.
Total assets     ₩ 26,572
Total liabilities     14,940
Operating revenues     46,608
Profit (loss) for the year     ₩ (2,516)
KT music contents fund no.1 [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KT Music Contents Fund No.1
Total assets     ₩ 4,844
Total liabilities     1,525
Operating revenues     243
Profit (loss) for the year     ₩ 84
KT Sat Inc. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary   KT Sat Inc. KT Sat Inc.
Total assets   ₩ 593,616 ₩ 630,740
Total liabilities   34,169 92,791
Operating revenues   174,750 173,693
Profit (loss) for the year   ₩ 20,830 ₩ 14,753
KBTO sp.zo.o. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KBTO sp.z o.o.
Total assets     ₩ 438
Total liabilities     117
Operating revenues     490
Profit (loss) for the year     ₩ (2,823)
Autopion Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     Autopion Co., Ltd.
Total assets     ₩ 4,903
Total liabilities     4,961
Operating revenues     6,174
Profit (loss) for the year     ₩ (2,459)
Korea Telecom China Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     Korea Telecom China Co., Ltd.
Total assets     ₩ 381
Total liabilities     21
Operating revenues     618
Profit (loss) for the year     ₩ (492)
KT Hopemate [member]      
Disclosure of subsidiaries [line items]      
Subsidiary   KT Hopemate KT Hopemate
Total assets   ₩ 6,311 ₩ 3,720
Total liabilities   2,978 2,787
Operating revenues   12,538 5,239
Profit (loss) for the year   ₩ 116 ₩ (13)
KT M mobile Inc. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary   KT M Mobile Inc. KT M Mobile Inc.
Total assets   ₩ 144,175 ₩ 129,011
Total liabilities   40,749 27,281
Operating revenues   204,641 163,472
Profit (loss) for the year   ₩ 5,918 ₩ (3,617)
GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co.
Total assets     ₩ 5,703
Total liabilities     1,165
Operating revenues     333
Profit (loss) for the year     ₩ 83
KT Dutch B.V. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KT Dutch B.V.
Total assets     ₩ 29,585
Total liabilities     10,109
Operating revenues     26,782
Profit (loss) for the year     ₩ 6,061
KT Belgium [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KT Belgium
Total assets     ₩ 87,608
Total liabilities     0
Operating revenues     (81)
Profit (loss) for the year     ₩ (81)
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.)
Total assets ₩ 141,463 ₩ 185,850 ₩ 138,220
Total liabilities 89,853 144,832 102,963
Operating revenues 258,435 284,998 346,040
Profit (loss) for the year ₩ 10,302 ₩ 366 ₩ (8,461)
Nasmedia Co Ltd [member]      
Disclosure of subsidiaries [line items]      
Subsidiary Nasmedia Co., Ltd. Nasmedia Co., Ltd. Nasmedia Co., Ltd.
Total assets ₩ 516,945 ₩ 490,394 ₩ 422,039
Total liabilities 275,730 268,618 221,371
Operating revenues 153,211 125,876 113,136
Profit (loss) for the year 27,691 ₩ 27,120 ₩ 23,134
KT M Hows Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KT M Hows Co., Ltd.
Total assets     ₩ 104,704
Total liabilities     76,315
Operating revenues     44,860
Profit (loss) for the year     ₩ 6,935
KTGDH Co., Ltd. (KTSB Data service) [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KTGDH Co., Ltd. (KTSB Data Service)
Total assets     ₩ 11,003
Total liabilities     1,669
Operating revenues     4,282
Profit (loss) for the year     ₩ 538
KT Philippines [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary   KT Philippines  
Total assets   ₩ 3,641  
Total liabilities   1,243  
Operating revenues   0  
Profit (loss) for the year   ₩ 0  
KT Sports Inc.[member]      
Disclosure of subsidiaries [line items]      
Subsidiary   KT Sports Inc.  
Total assets   ₩ 29,524  
Total liabilities   19,740  
Operating revenues   67,612  
Profit (loss) for the year   ₩ (2,039)  
Next Connect PFV [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary   Next Connect PFV  
Total assets 624,734    
Total liabilities 277,967    
Operating revenues 3    
Profit (loss) for the year ₩ (3,712)