| Document and Entity Information | Dec. 09, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001718108 |
| Document Type | 8-K |
| Document Period End Date | Dec. 9, 2021 |
| Entity Registrant Name | SURFACE ONCOLOGY, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38459 |
| Entity Tax Identification Number | 46-5543980 |
| Entity Address, Address Line One | 50 Hampshire Street |
| Entity Address, Address Line Two | 8th |
| Entity Address, Address Line Three | Floor |
| Entity Address, City or Town | Cambridge |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02139 |
| City Area Code | (617) |
| Local Phone Number | 714-4096 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common stock, $0.0001 |
| Trading Symbol | SURF |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | true |
