PURPOSE: To improve a shock absorbing effect by arranging short-circuit orifices and throttle orifices between an inner cylinder and a sliding cylinder, opening/ closing these, supplying a pressure liquid to the inner cylinder from the sliding cylinder by a pump, and accumulating and effectively using energy at required time.

CONSTITUTION: At ordinary time, a control piston 16 is held in an abutting member 19 by a spring 18. At this time, a first orifice 13 of a sliding member 9 coincides with throttle orifices 11 of a dip rod 2, and a second orifice 14 is similarly deviated from short-circuit orifices 12. While, at required time, the control piston 16 is pushed down, and the first orifice 13 and the throttle orifices 11 do not coincide with each other. As a result, a pump 24 supplies a pressure fluid to the dip rod 2 from a sliding rod 3, and the sliding rod 3 retracts into a strut 1 to increase pressure of compressed gas in the dip rod 2. When the control piston 16 is pushed down further, the pressure liquid flows to a lower chamber 7 from an upper chamber 6 of the sliding rod 3 without being throttled to quickly extend a shock absorber.