PURPOSE: To surely prevent a pumping reaction from increasing by providing an outlet passage for guiding a working fluid to a high pressure chamber and a going and returning passage for guiding the working fluid in the high pressure chamber to a working fluid chamber in a shock absorber and a variable throttle device for controlling the level of communicating of the going and returning passage in the middle way thereof.

CONSTITUTION: By increasing the capacity of the pump chamber 54 of a pump 140 during the extension stroke of a shock absorber, a suction valve 64 is opened and oil is sucked from a low pressure chamber. By increasing a pressure in the pump chamber 54 during the contraction stroke of the shock absorber, a discharge valve 80 is opened and oil in the pump chamber 54 is discharged to the liquid chamber 124 of an accumulator 18. In this case, since the increase/ decrease of damping force is controlled by driving a variable throttle valve 132 by means of an actuator 134 and oil is supplied without passing through the variable throttle valve 132 during the contraction stroke of the shock absorber, the increase of a pumping reaction is prevented.