To facilitate the arrangement of a pressure medium accumulator on the inside of a vehicle by forming an inside support member, an outside support member and a covering member for diaphragm as an accumulator element out of the flexible material such as a hose.

A pressure medium accumulator 2 as an accumulator element is formed of a hose-like diaphragm 10, an inside support member 11, which does not hinder the flow of the pressure medium, an air permeable outside support member 12, and a cover part 13. The diaphragm 10 is formed into a relatively thin film so that the diameter of the diaphragm 10 is reduced at 10% when the pressure lowering from outside to inside is generated in a range of 0.2 bar, for example. Perfect contraction of the diaphragm 10 is avoided by the coil-like support member 11 formed of a steel wire laid inside. The outside support member 12 formed of a flexible hose is unified with the inside support member 11, the diaphragm 10 and the cover part 13 formed of a wire mesh, and the accumulator 2 can be easily bent for arrangement on the inside of a vehicle.