A diamond eccentric drill bit comprises a cylindrical main body (1) consisting of a hexagonal shank (2) and a cylindrical body (3), and securely installed via the hexagonal shank (2) on a tool. A diamond drill bit (4) is fixed above the cylindrical body (3) of the cylindrical main body (1). The diamond drill bit (4) is annular. An eccentric part (6) is disposed in the annular diamond drill bit (4). The diamond eccentric drill bit is simple and easy to operate, requires no water in operation, has low requirement for machine power, can be used in a rechargeable tool, and can significantly increase safety of an operator.