To prevent change of damping force characteristics and production of abnormal sound even though air is entrapped into the inside of a pressure chamber and a channel in assembling.

Pressure chamber is vertically partitioned into upper pressure chambers 15a, 16a and lower pressure chambers 15b, 16b by rotary vanes 2a, 2b, disk valves 26a, 27a generating damping force by limitedly allowing fluid flow in the direction of the lower pressure chambers 15b, 16b are arranged on the way of a pair of second communicating passages C mutually communicating pressure chambers whose voluminal changes are reversed through the rotary vanes 2a, 2b, opening parts to the second communicating passages C are arranged in the uppermost parts of the upper pressure chambers 15a, 16a, a reservoir chamber R that air is entrapped is arranged on a side further downstream from the disk valves, 26a, 27a, the lower fluid chamber Rb side of the reservoir chamber R is connected to the lower pressure chambers 15b, 16b, and check valves 28, 29 allowing only fluid flow in the direction of the lower pressure chambers 15b, 16b are interposed among the reservoir chamber R and the lower pressure chambers 15b, 16b.