| Document and Entity Information | May 14, 2024 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001891856 |
| Document Type | 8-K |
| Document Period End Date | May 14, 2024 |
| Entity Registrant Name | GEN Restaurant Group, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-41727 |
| Entity Tax Identification Number | 87-3424935 |
| Entity Address, Address Line One | 11480 South Street |
| Entity Address, Address Line Two | Suite 205 |
| Entity Address, City or Town | Cerritos |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 90703 |
| City Area Code | (562) |
| Local Phone Number | 356-9929 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Class A Common stock, par value $0.001 per share |
| Trading Symbol | GENK |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
