| Cover | Sep. 29, 2023 |
| Document Information [Line Items] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Amendment Description | On October 5, 2023, NKGen Biotech, Inc. (f/k/a Graf Acquisition Corp. IV) (the "Company") filed a Current Report on Form 8-K (the "Original 8-K") with the Securities Exchange Commission ("SEC") to report, among other events, the consummation of the Business Combination (as defined in the Original 8-K) on September 29, 2023. The Company is filing the Amendment No.1 on Form 8-K/A (this "Amendment") to amend the Original 8-K and to replace the Unaudited Pro Forma Condensed Combined Financial Information of the Company as of and for the six months ended June 30, 2023 and the year ended December 31, 2022, included as Exhibit 99.3. |
| Document Period End Date | Sep. 29, 2023 |
| 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 St |
| 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 |
