A body-side cushion structural body attached to a body and a piston-side cushion structural body integrally moving with a piston are disposed outside the body, a cushion rod is disposed on either one of the cushion structural bodies, while a rod fitting hole is disposed in the other cushion structural body, a cushion packing is disposed at a spout portion of the rod fitting hole, and moreover, a throttle valve that discharges air in the rod fitting hole to the outside with flow-rate adjustment is disposed so as to configure an air cushion mechanism that stops the piston in a buffering manner.