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Cover - USD ($)
 12 Months Ended
Jun. 30, 2023
Oct. 06, 2023
Dec. 31, 2022
Document Type 10-K    
Amendment Flag false    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Jun. 30, 2023    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2023    
Current Fiscal Year End Date --06-30    
Entity File Number 000-55710    
Entity Registrant Name NioCorp Developments Ltd.    
Entity Central Index Key 0001512228    
Entity Tax Identification Number 98-1262185    
Entity Incorporation, State or Country Code A1    
Entity Address, Address Line One 7000 South Yosemite Street    
Entity Address, Address Line Two Suite 115    
Entity Address, City or Town Centennial    
Entity Address, State or Province CO    
Entity Address, Postal Zip Code 80112    
City Area Code (720)    
Local Phone Number 334-7066    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 190,700,000
Entity Common Stock, Shares Outstanding   32,913,419  
Auditor Name BDO USA, P.C.; Spokane, Washington; PCAOB ID#    
Auditor Location Spokane, Washington    
Auditor Firm ID 243    
Common Shares Without Par Value [Member]      
Title of 12(b) Security Common Shares, without par value    
Trading Symbol NB    
Security Exchange Name NASDAQ    
Warrants Each Exercisable for 1.11829212 Common Shares [Member]      
Title of 12(b) Security Warrants, each exercisable for 1.11829212 Common Shares    
Trading Symbol NIOBW    
Security Exchange Name NASDAQ