To improve responsiveness of a buffer and regulate a damping force throughout a wide range.

A hollow part and a plurality of through-holes are formed in a piston rod 24. Further, A rotatable rotary valve 32 is inserted in a hollow part from the outside and a through-hole is opened and closed by the rotary valve 32. A piston rod is provided on an outer peripheral surface with a piston 23, a first subvalve 26 and a first check valve 25 arranged on one side, and a second subvalve 27 and a second check valve 28 arranged on the other side. Oil in a first oil chamber A is caused to flow, in order to the check valve 25, a through-hole, a passage in a rotary valve 32, and the second subvalve 27 and is moved to a second oil chamber B. Oil in the second oil chamber B is caused to flow, in order, to the second check valve 28, a through-hole, a passage 32g in the rotary valve 32, and a first subvalve 26 and is moved to the first oil chamber A.