| Cover | May 25, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 25, 2022 |
| 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 | 639-4647 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | true |
