The invention provides an automatic screw locking device for a plastic case circuit breaker base. The automatic screw locking device for the plastic case circuit breaker base comprises a base input wire, a base output wire, a first screw locking circulating wire and a second screw locking circulating wire; the starting end of the first screw locking circulating wire is in butt joint with the baseinput wire; the tail end of the first screw locking circulating wire is in butt joint with a base transferring mechanism and the starting end of the second screw locking circulating wire through a base transferring mechanism; the tail end of the second screw locking circulating wire is in butt joint with the base output wire; a plurality of first screw feeding mechanisms are arranged on one side of the first screw locking circulating wire, and a plurality of first automatic screw locking mechanisms are arranged on the other side of the first screw locking circulating wire; a plurality of second screw feeding mechanisms are arranged on one side of the second screw locking circulating wire, and a plurality of second automatic screw locking mechanisms are arranged on the other side of the second screw locking circulating wire. According to the automatic screw locking device for the plastic case circuit breaker base, combined screws, of machine tooth belt flat gaskets and spring gaskets, at different positions of the plastic case circuit breaker base can be automatically locked, automatic one-time locking is achieved, the locking success rate is 100%, the automation degree is high, toomuch manual participation is not needed in the whole process, and the production efficiency is greatly improved.