A linear actuator includes a screw shaft rotatably supported within a housing with play in motion in the axial direction of the screw shaft, and a cushioning stopper disposed between the housing and the screw shaft and elastically deformable to absorb a force acting from the screw shaft to the housing when the screw shaft is forced to move relative to the housing in the axial direction within the range of the play at an abutment of a rod with an obstacle or stopper. When the rod is stopped moving, the motor current increases with the degree of elastic deformation of the cushioning stopper. An overload sensor cuts off the supply of power to an electric motor when excessive current in the motor is detected.