The invention discloses a screw trimming device comprising a guide rail (1), a guide rail pressing plate (2), an electromagnet (5), a screw pressing plate (6), a bolt (7), a nut (8) and a spring (9); the guide rail pressing plate (2) is arranged above the guide rail (1); an armature column of the electromagnet (5) applies pressure to the screw pressing plate (6) when being electrified to work so that the screw pressing plate (6) is bounced, and the armature column of the electromagnet (5) departs from the screw pressing plate (6) when being diselectrified; the screw pressing plate (6) is installed on the bolt (7); the screw pressing plate (6) is arranged between the nut (8) and the spring (9); and the spring (9) applies elastic force to the screw pressing plate (6) so that the screw pressing plate (6) is inclined to press a second screw arranged at the tail end of the guide rail (1). The screw trimming device is convenient for operators to operate and can avoid absorption of the screwdue to bit magnetism and the bouncing and splashing around of the second screw due to the vibration of a screw machine.