| Document and Entity Information | Feb. 03, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | INTEVAC INC |
| Amendment Flag | false |
| Entity Central Index Key | 0001001902 |
| Document Type | 8-K |
| Document Period End Date | Feb. 3, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 0-26946 |
| Entity Tax Identification Number | 94-3125814 |
| Entity Address, Address Line One | 3560 Bassett Street |
| Entity Address, City or Town | Santa Clara |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 95054 |
| City Area Code | (408) |
| Local Phone Number | 986-9888 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock ($0.001 par value) |
| Trading Symbol | IVAC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
