The invention discloses an automatic screw tightening machine for a circuit breaker base. The automatic screw tightening machine for the circuit breaker base comprises a rack. A conveying mechanism isarranged in the middle layer of the rack. A pressing mechanism is arranged above the conveying mechanism. Four screw supplying mechanisms are arranged above the pressing mechanism. A working platformis arranged below the conveying mechanism. A first supporting frame and a second supporting frame are fixed to the working platform and separately located outside the two sides of the conveying mechanism. Two lead screws are horizontally connected between the first supporting frame and the second supporting frame and located below a positioning plate. A lead screw motor is arranged at the end ofone lead screw. The lead screws are slidably sleeved with a screw reversing mechanism. A screw feeding mechanism is arranged on the inner side face of the second supporting frame. A screw locking mechanism is arranged below the screw reversing mechanism. The automatic screw tightening machine for the circuit breaker base is compact in structure, reliable in work and high in working efficiency.