To miniaturize a stopper switch and especially reduce a diameter by elaborately providing a cushion means on the stopper switch in extremely simple structure.

A first cushion means to compress air in a cylinder 1b by a piston 5 to move in the cylinder 1b as a detection body A makes contact with a head end of a piston shaft 4 and displaced, a second cushion means on which an elastic member 7 starts to be compressed slightly before the piston 5 makes contact with a stop surface 1c of the piston 5 provided on the cylinder 1b, a third cushion means to keep compressing a compression coil spring 9 as the detection body A makes contact with the head end of the piston shaft 4 and is displaced and a switch means 3 to work immediately before the piston 5 makes contact with the stop surface 1c of the piston 5 are provided.