To promote sealing characteristics between a piston rod and a sealing member by providing a resilient portion and a cushoning portion between piston member and projected portion.

In a cylinder 3, a seal member accomodating groove 6 is formed. In this seal member accomodating groove 6, a packing 8 made of nitrile rubber, etc., for instance, is stored. In the packing 8, a packing recessed portion 8a, internal circumferential packing 8b and an outer circumferential packing 8c are formed. In a rod 2, a piston support portion 12 as projected part is provided. In the piston support portion 12, a piston 4 is provided as the piston member, through a spring 16 as the resilient portion, and a damper 14 as the cushioning portion. This piston support portion 12 and the piston 4 are stored in a piston receiving part 10 provided in the cylinder 3. Further, a clearance 18 is provided between the rod 2 and the cylinder 3.