| Cover | Jan. 02, 2024 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jan. 02, 2024 |
| Entity File Number | 001-40427 |
| Entity Registrant Name | NKGen Biotech, Inc. |
| Entity Central Index Key | 0001845459 |
| Entity Tax Identification Number | 86-2191918 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 3001 Daimler Street |
| Entity Address, City or Town | Santa Ana |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92705 |
| City Area Code | 949 |
| Local Phone Number | 396-6830 |
| 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 | false |
| Common Stock [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock, $0.0001 par value per share |
| Trading Symbol | NKGN |
| Security Exchange Name | NASDAQ |
| Warrant [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrants, each whole warrant exercisable for one share of Common Stock at an exercise price of $11.50 per share |
| Trading Symbol | NKGNW |
| Security Exchange Name | NASDAQ |
