To solve the problems wherein long working distance is required and buffer force causes unevenness due to fluctuation of a hole diameter because buffer force is obtained for the first time when air is compressed to some extent in a pneumatic damper utilizing resistance generated when air comes out of a minute hole.

Volume in a cylinder chamber is made almost void before working, and a ventilation hole for air is blocked when working to realize a structure in which the cylinder chamber becomes a vacuum condition when working. Buffering acts from the beginning of working and there is no ventilation hole to reduce unevenness of buffer force.