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General Information - Summary of Consolidated Subsidiaries (Detail) - KRW (₩)
₩ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Disclosure of subsidiaries [line items]      
Total assets ₩ 42,791,647 ₩ 40,989,810  
Total liabilities 24,249,073 22,577,114  
Operating revenues 26,287,201 25,638,855 ₩ 24,898,005
Profit (loss) for the year ₩ 972,182 ₩ 1,385,635 ₩ 1,459,395
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 ₩ 64,178 ₩ 47,734 ₩ 54,219
Total liabilities 63,452 47,498 53,316
Operating revenues 81,645 76,135 81,434
Profit (loss) for the year ₩ 821 ₩ (614) ₩ (3,095)
KT Submarine Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary   KT Submarine Co., Ltd. KT Submarine Co., Ltd.
Total assets   ₩ 120,255 ₩ 110,390
Total liabilities   7,884 10,736
Operating revenues   42,848 31,374
Profit (loss) for the year   ₩ (12,126) ₩ (3,183)
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 ₩ 375,596 ₩ 370,004 ₩ 363,224
Total liabilities 235,947 230,965 233,797
Operating revenues 527,015 517,406 515,456
Profit (loss) for the year ₩ 5,728 ₩ 4,267 ₩ 3,985
KT Alpha Co Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Alpha Co., Ltd.    
Type of Business Data communication    
Location Korea    
Controlling percentage ownership 73.00% 73.00%  
Closing month December    
Total assets ₩ 443,639    
Total liabilities 191,254    
Operating revenues 437,308    
Profit (loss) for the year ₩ 19,352    
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.)
Total assets   ₩ 406,236 ₩ 390,671
Total liabilities   172,211 172,767
Operating revenues   516,737 471,870
Profit (loss) for the year   ₩ 13,115 ₩ (8,692)
KT Service Bukbu Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Service Bukbu Co., Ltd. KT Service Bukbu Co., Ltd. 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 ₩ 63,760 ₩ 74,673 ₩ 59,341
Total liabilities 55,360 65,820 54,070
Operating revenues 242,119 252,304 231,602
Profit (loss) for the year ₩ 1,212 ₩ 3,227 ₩ 1,128
KT Service Nambu Co., Ltd. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Service Nambu Co., Ltd. KT Service Nambu Co., Ltd. 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 ₩ 71,576 ₩ 80,450 ₩ 62,513
Total liabilities 58,745 66,479 52,695
Operating revenues 291,170 301,720 271,174
Profit (loss) for the year ₩ 1,354 ₩ 3,067 ₩ 1,430
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.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 ₩ 6,352,878 ₩ 5,666,075 ₩ 3,933,427
Total liabilities 4,722,432 4,109,200 2,481,004
Operating revenues 4,027,450 3,897,090 3,580,970
Profit (loss) for the year ₩ 76,545 ₩ 148,341 ₩ 120,308
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 72.20% 69.70%  
Closing month December    
H&C Network [member]      
Disclosure of subsidiaries [line items]      
Subsidiary H&C Network H&C Network H&C Network Co., Ltd.
Type of Business Call center for financial sectors    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 81,107 ₩ 82,737 ₩ 88,616
Total liabilities 4,863 6,640 4,993
Operating revenues 27,205 27,392 227,604
Profit (loss) for the year ₩ 1,814 ₩ 992 ₩ 11,995
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 63.90% 61.30%  
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 91.60% 95.60%  
Closing month December    
Total assets ₩ 393,667 ₩ 401,932 ₩ 341,358
Total liabilities 202,067 228,474 199,831
Operating revenues 727,477 723,161 632,899
Profit (loss) for the year ₩ 33,971 ₩ 30,941 ₩ 21,464
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 ₩ 258,477 ₩ 255,310 ₩ 241,377
Total liabilities 209,075 204,336 203,051
Operating revenues 695,856 730,802 710,634
Profit (loss) for the year ₩ 3,783 ₩ 8,105 ₩ 3,496
GENIE Music Corporation [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary GENIE Music Corporation    
Type of Business Online music production and distribution    
Location Korea    
Controlling percentage ownership 36.00% 36.00%  
Closing month December    
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 ₩ 50,750 ₩ 38,684 ₩ 32,511
Total liabilities 28,431 22,553 25,402
Operating revenues 101,428 83,085 70,212
Profit (loss) for the year ₩ 8,457 ₩ 4,607 ₩ 1,637
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 ₩ 46,839 ₩ 42,011 ₩ 36,741
Total liabilities 26,012 25,416 26,053
Operating revenues 101,422 83,330 71,940
Profit (loss) for the year ₩ 5,749 ₩ 5,035 ₩ 2,016
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 ₩ 1,220,842 ₩ 1,359,166 ₩ 1,275,645
Total liabilities 479,369 503,679 469,694
Operating revenues 1,034,342 1,038,468 772,950
Profit (loss) for the year ₩ (109,407) ₩ 20,941 ₩ 62,309
KT Skylife [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Skylife    
Type of Business Satellite TV    
Location Korea    
Controlling percentage ownership 50.60% 50.20%  
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 ₩ 2,746,546 ₩ 2,480,333 ₩ 2,370,940
Total liabilities 1,121,970 833,842 791,884
Operating revenues 511,018 478,188 577,578
Profit (loss) for the year ₩ 871 ₩ 58,780 ₩ 213,203
KT Investment Management Inc. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Investment Management Inc.    
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. 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 ₩ 7,760 ₩ 12,059 ₩ 11,464
Total liabilities 1,501 1,596 1,560
Operating revenues 4,346 4,323 4,423
Profit (loss) for the year ₩ 648 ₩ 451 ₩ 553
KT Sat Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Sat Co., Ltd. KT Sat Co., Ltd.  
Type of Business Satellite communication business    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 699,607 ₩ 677,980  
Total liabilities 88,524 89,644  
Operating revenues 182,274 185,313  
Profit (loss) for the year ₩ 30,502 ₩ 28,073  
Nasmedia, Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Nasmedia Co., Ltd. Nasmedia Co., Ltd. Nasmedia Co., Ltd.
Type of Business Solution provider and IPTV advertisement sales business    
Location Korea    
Controlling percentage ownership 44.10% 44.00%  
Closing month December    
Total assets ₩ 513,311 ₩ 516,945 ₩ 490,394
Total liabilities 262,336 275,730 268,618
Operating revenues 147,934 153,210 125,876
Profit (loss) for the year ₩ 17,703 ₩ 27,691 ₩ 27,120
KT Sports Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Sports Co., Ltd. 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 ₩ 26,615 ₩ 28,220  
Total liabilities 11,299 15,461  
Operating revenues 66,309 65,350  
Profit (loss) for the year ₩ (12,386) ₩ (7,302)  
KT 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 ₩ 5,558 ₩ 15,718 ₩ 14,985
Total liabilities 1,772 277 278
Operating revenues 534 1,040 253
Profit (loss) for the year ₩ (992) ₩ 735 ₩ (30)
KT-Michigan global contents fund [member]      
Disclosure of subsidiaries [line items]      
Subsidiary   KT-Michigan Global Content Fund KT-Michigan Global Contents Fund
Total assets   ₩ 2,371 ₩ 3,552
Total liabilities   27 112
Operating revenues   33 13,592
Profit (loss) for the year   ₩ (1,095) ₩ 10,032
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% 34.10%  
Closing month December    
Total assets ₩ 434,900 ₩ 419,726 ₩ 416,750
Total liabilities 234,850 228,618 234,172
Operating revenues 1,035,911 1,031,010 968,499
Profit (loss) for the year ₩ 15,804 ₩ 17,634 ₩ 19,034
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% 33.30%  
Closing month December    
Total assets ₩ 447,609 ₩ 396,208 ₩ 369,361
Total liabilities 243,519 199,204 177,619
Operating revenues 593,162 536,229 487,801
Profit (loss) for the year ₩ 13,922 ₩ 15,917 ₩ 24,944
KT M Mobile Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT M Mobile Co., Ltd. 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 ₩ 176,838 ₩ 152,114  
Total liabilities 69,317 49,816  
Operating revenues 301,049 262,918  
Profit (loss) for the year ₩ 5,605 ₩ 4,731  
Next Connect PFV Inc. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary Next Connect PFV   Next Connect PFV Inc.
Total assets ₩ 946,687   ₩ 518,441
Total liabilities 629,809   167,963
Operating revenues 0   0
Profit (loss) for the year ₩ (29,889)   ₩ (6,519)
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 ₩ 83,638 ₩ 103,354 ₩ 87,366
Total liabilities 57,420 79,182 66,108
Operating revenues 24,976 15,136 21,040
Profit (loss) for the year ₩ 2,180 ₩ 2,840 ₩ (697)
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    
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 ₩ 134,847 ₩ 126,721 ₩ 125,860
Total liabilities 313,787 267,369 236,389
Operating revenues 26,788 30,834 23,328
Profit (loss) for the year ₩ (57,628) ₩ (27,467) ₩ (28,770)
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 ₩ 10,763 ₩ 10,972 ₩ 11,539
Total liabilities 1,983 905 2,812
Operating revenues 8,287 8,049 6,942
Profit (loss) for the year ₩ 128 ₩ 1,274 ₩ 823
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 ₩ 2,015 ₩ 1,888 ₩ 1,474
Total liabilities 3,341 3,141 2,633
Operating revenues 2,793 3,263 1,298
Profit (loss) for the year ₩ (110) ₩ 226 ₩ (142)
East Telecom LLC [member]      
Disclosure of subsidiaries [line items]      
Subsidiary East Telecom LLC 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 ₩ 48,483 ₩ 42,691 ₩ 35,904
Total liabilities 22,632 21,645 22,088
Operating revenues 30,350 27,030 11,960
Profit (loss) for the year ₩ 7,723 ₩ 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 ₩ 6,013 ₩ 5,945 ₩ 4,884
Total liabilities 701 843 101
Operating revenues 8,928 8,070 6,508
Profit (loss) for the year ₩ 133 ₩ 37 ₩ 201
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 ₩ 11,142 ₩ 10,505 ₩ 6,613
Total liabilities 5,121 4,768 1,346
Operating revenues 19,373 20,413 18,825
Profit (loss) for the year ₩ 143 ₩ 51 ₩ 1,313
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 KT Huimangjieum  
Type of Business Manufacturing    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 8,073 ₩ 6,984  
Total liabilities 2,715 2,582  
Operating revenues 17,687 22,860  
Profit (loss) for the year ₩ 1,012 ₩ 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.    
Type of Business Contents and software development and supply    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KT Engineering Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Engineering Co., Ltd.    
Type of Business Telecommunication facility construction andmaintenance    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 160,243    
Total liabilities 104,005    
Operating revenues 262,063    
Profit (loss) for the year ₩ 5,327    
KT Studio Genie Co Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Studio Genie Co., Ltd. KT Studio Genie Co., Ltd. KT Studio Genie Co., Ltd.
Type of Business Data communication service and datacommunication construction business    
Location Korea    
Controlling percentage ownership 90.90% 90.90%  
Closing month December    
Total assets ₩ 989,187 ₩ 987,270 ₩ 648,534
Total liabilities 259,413 268,911 276,933
Operating revenues 542,955 723,580 90,047
Profit (loss) for the year ₩ 13,507 ₩ 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. Lolab Co., Ltd.
Type of Business Truck transportation and truckingarrangement business    
Location Korea    
Controlling percentage ownership 79.80% 79.80%  
Closing month December    
Total assets ₩ 42,744 ₩ 35,091 ₩ 26,726
Total liabilities 37,838 17,247 897
Operating revenues 173,035 74,881 2,107
Profit (loss) for the year ₩ (12,938) ₩ (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 30.20% 38.60%  
Closing month December    
KT ES Pte Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT ES Pte. Ltd. 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 ₩ 117,009 ₩ 240,721 ₩ 240,331
Total liabilities 90,392 88,640 80,597
Operating revenues 87,865 78,815 15,157
Profit (loss) for the year ₩ (124,850) ₩ (23,957) ₩ (6,355)
Epsilon Global Communications Pte. Ltd [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Epsilon Global CommunicationsPTE. Ltd.    
Type of Business Network service industry    
Location Singapore    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Epsilon Telecommunications (SP) Pte Ltd [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 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 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    
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    
Nasmedia KT Alpha Future Growth Strategic Investment Fund [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Nasmedia-KT Alpha Future GrowthStrategic Investment Fund    
Type of Business Investment fund    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Altimedia Corporation [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Altimedia Corporation 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 ₩ 48,381 ₩ 44,861 ₩ 32,338
Total liabilities 12,374 15,777 9,742
Operating revenues 45,035 47,203 6,968
Profit (loss) for the year ₩ 7,352 ₩ 6,035 ₩ 1,037
Altimidia B.V. (formerly Alticast B.V.) [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Altimidia B.V.(formerly 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    
Altimidia Vietnam (formerly Alticast Company Limited) [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Altimidia Vietnam(formerly Alticast Company Limited)    
Type of Business Software development and delivery    
Location Vietnam    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
KT RUS LLC [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT RUS LLC KT RUS LLC  
Type of Business Foreign investment business    
Location Russia    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 501 ₩ 967  
Total liabilities 10 16  
Operating revenues 1 5  
Profit (loss) for the year ₩ (378) ₩ (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% 75.00%  
Closing month December    
KTP SERVICES INC. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KTP SERVICES INC. KTP SERVICES INC.  
Type of Business Fixed line telecommunication business    
Location Philippines    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 2,967 ₩ 3,832  
Total liabilities 919 2,044  
Operating revenues 671 776  
Profit (loss) for the year ₩ 235 ₩ (255)  
KT Cloud Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Cloud Co., Ltd. kt cloud Co., Ltd.  
Type of Business Information and communications development    
Location Korea    
Controlling percentage ownership 92.70% 100.00%  
Closing month December    
Total assets ₩ 1,983,972 ₩ 1,348,684  
Total liabilities 503,241 245,872  
Operating revenues 679,825 432,118  
Profit (loss) for the year ₩ 63,956 ₩ 14,712  
KT DX Vietnam Company Limited [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT DX Vietnam Company Limited KT DX Vietnam Company Limited  
Type of Business Software development    
Location Vietnam    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets ₩ 1,694 ₩ 1,815  
Total liabilities 102 6  
Operating revenues 82 0  
Profit (loss) for the year ₩ (207) ₩ 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% 80.90%  
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% 67.00%  
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 42.60% 41.20%  
Closing month December    
open cloud lab Co., Ltd (formerly SPARK AND ASSOCIATES INC.) [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary open cloud lab Co., Ltd(formerly SPARK AND ASSOCIATES INC.)    
Type of Business IT consulting service and Telecommunication equipment sales    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
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)
KT Sat Inc. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KT Sat Inc.
Total assets     ₩ 593,616
Total liabilities     34,169
Operating revenues     174,750
Profit (loss) for the year     ₩ 20,830
KT Hopemate [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KT Hopemate
Total assets     ₩ 6,311
Total liabilities     2,978
Operating revenues     12,538
Profit (loss) for the year     ₩ 116
KT M mobile Inc. [member]      
Disclosure of subsidiaries [line items]      
Subsidiary     KT M Mobile Inc.
Total assets     ₩ 144,175
Total liabilities     40,749
Operating revenues     204,641
Profit (loss) for the year     ₩ 5,918
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.)
Total assets   ₩ 141,463 ₩ 185,850
Total liabilities   89,853 144,832
Operating revenues   258,435 284,998
Profit (loss) for the year   ₩ 10,302 ₩ 366
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
Next Connect PFV [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary Next Connect PFV Next Connect PFV  
Type of Business Residential building development and supply    
Location Korea    
Controlling percentage ownership 100.00% 100.00%  
Closing month December    
Total assets   ₩ 624,734  
Total liabilities   277,967  
Operating revenues   3  
Profit (loss) for the year   ₩ (3,712)  
KD Living, Inc. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KD Living, Inc    
Type of Business Residential building management    
Location Korea    
Controlling percentage ownership 100.00%    
Closing month December    
KT Healthcare Vina Co., Ltd. [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary KT Healthcare Vina Co., Ltd.    
Type of Business Medical service    
Location Vietnam    
Controlling percentage ownership 100.00%    
Closing month December    
Total assets ₩ 12,730    
Total liabilities 439    
Operating revenues 0    
Profit (loss) for the year ₩ (721)    
K-Realty Qualified Private Real Estate Investment Trust No. 1 [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary K-Realty Qualified Private Real Estate Investment Trust No. 1    
Type of Business Real estate management    
Location Korea    
Controlling percentage ownership 6.50%    
Closing month December    
Total assets ₩ 80,266    
Total liabilities 50,693    
Operating revenues 4,682    
Profit (loss) for the year ₩ (1,037)    
AQUA RETAIL VIETNAM COMPANY LIMITED [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary AQUA RETAIL VIETNAM COMPANY LIMITED    
Type of Business E-voucher issuance and trading business    
Location Vietnam    
Controlling percentage ownership 100.00%    
Closing month December    
Total assets ₩ 1,202    
Total liabilities 62    
Operating revenues 16    
Profit (loss) for the year ₩ (248)    
K-Realty Qualified Private Real Estate Investment Trust No. 4 [Member]      
Disclosure of subsidiaries [line items]      
Subsidiary K-Realty Qualified Private Real Estate Investment Trust No. 4    
Type of Business Real estate management    
Location Korea    
Controlling percentage ownership 93.90%    
Closing month December