An accumulator includes a bellows housed to freely expand and contract in a shell, a port part having a pressure fluid inflow port formed therein, and a self-sealing member arranged on a tip portion of the bellows to face the port part, in which when a pressure in the fluid chamber is lower than a predetermined pressure relative to an air chamber, the self-sealing member is allowed to abut onto a seal area of the port part to block the pressure fluid inflow port. The self-sealing member includes a resilient member arranged on a surface of a base material part, and an overhanging portion formed on the resilient member and allowed to abut onto the seal area for sealing. The port part includes a seal face having the seal area formed thereon, and a projecting portion arranged on a region other than the seal area on the seal face.