| Cover | Sep. 21, 2021 |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 21, 2021 |
| Entity File Number | 001-38325 |
| Entity Registrant Name | Hancock Jaffe Laboratories, Inc. |
| Entity Central Index Key | 0001661053 |
| Entity Tax Identification Number | 33-0936180 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 70 Doppler |
| Entity Address, City or Town | Irvine |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92618 |
| City Area Code | (949) |
| Local Phone Number | 261-2900 |
| 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 | true |
| Common Stock, par value $0.00001 per share | |
| Title of 12(b) Security | Common Stock, par value $0.00001 per share |
| Trading Symbol | HJLI |
| Security Exchange Name | NASDAQ |
| Warrant to Purchase Common Stock | |
| Title of 12(b) Security | Warrant to Purchase Common Stock |
| Trading Symbol | HJLIW |
| Security Exchange Name | NASDAQ |
