ACCUMULATOR

Provided is an accumulator, which: is capable of reducing the pressure difference that is generated by differences in coefficients of thermal expansion when liquid trapped in the liquid chamber and a sealed gas undergo thermal expansion during zero-down, thereby limiting the occurrence of plastic deformation in the bellows; and has a structure in which the parts are small and few in number. To achieve said purpose, the accumulator has a sealing member held on the port hole-side of the bellows cap via a seal holder. When operation of the machine is stopped and the pressure inside the pressure piping decreases, the sealing member contacts the sealing section and closes the liquid chamber. If liquid trapped in the liquid chamber when the liquid chamber is closed undergoes thermal expansion, the bellows cap moves in the direction away from the sealing section while the sealing member is still in contact with the sealing section. Since the sealing member is a rigid plate, the outer circumferential surface of which is covered by a flexible section obtained from a rubber-like elastic body, the flexible section allows relative movement of the bellows cap by undergoing shear deformation as a result of engagement with the seal holder.