LINEAR MOTION ACTUATOR

A linear motion actuator has a ball screw device having a screw shaft, a nut, and a plurality of balls, a piston mounted on one end of the screw shaft, and a stroke limiting mechanism setting an operation starting point in time of the screw shaft toward a first direction pointed by the one end. The nut has one end face directed to the first direction and a protruding part protruding from the one end face.