| Document and Entity Information | Aug. 16, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001716621 |
| Document Type | 8-K |
| Document Period End Date | Aug. 16, 2021 |
| Entity Registrant Name | Ra Medical Systems, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38677 |
| Entity Tax Identification Number | 38-3661826 |
| Entity Address, Address Line One | 2070 Las Palmas Drive |
| Entity Address, City or Town | Carlsbad |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92011 |
| City Area Code | 760 |
| Local Phone Number | 804-1648 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.0001 per share |
| Trading Symbol | RMED |
| Security Exchange Name | NYSEAMER |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
