An accumulator comprising: a bellows comprising a metallic bellows body forming a generally cylindrical shape whose both upper and lower ends are opened and a metallic cap forming a disc shape, the bellows body having a plurality of outer annular ridge portions and a plurality of inner annular ridge portions and configured to be capable of expanding and contracting, and a housing being provided with a bottomed cylindrical shell whose lower end opens and an oil port member which is welded and fixed thereto so as to close the lower end of the shell, the oil port member having a fluid supply port, wherein the bellows body is welded and fixed to an inner surface of the oil port member so as to close a fixed end constituting the lower end thereof, and the bellows cap is welded and fixed thereto in a state that an annular guard ring is sandwiched therebetween so as to close a loose end constituting the upper end thereof, an interior of the housing being partitioned in a sealed state into an inside and an outside of the bellows, wherein the outer annular ridge portions are divided into at least a first sector and a second sector which are distributed in an expansion and contraction direction of the bellows such that the second sector is positioned between the first sector and the fixed end, and the outer annular ridge portions included in the first sector have an outer diameter smaller than that of the outer annular ridge portions included in the second sector, wherein an annular damping ring is attached to an outer peripheral portion of the bellows cap such that the bellows body and the bellows cap do not directly contact against an inner wall surface of the shell, an outer peripheral surface of the damping ring and the inner wall surface of the shell are slightly spaced in a radial direction and can smoothly slide without impeding expansion and contraction of the bellows, wherein the loose end of the bellows body is slightly spaced in the radial direction from the outer peripheral surface of the damping ring and the inner wall surface of the shell, and as a result when the accumulator receives external vibration, the outer peripheral surface and the inner wall surface repeat abutment while slightly vibrating in the radial direction within the vibrating shell. the outer annular ridge portions are divided into at least a first sector and a second sector which are distributed in an expansion and contraction direction of the bellows such that the second sector is positioned between the first sector and the fixed end, and the outer annular ridge portions included in the first sector have an outer diameter smaller than that of the outer annular ridge portions included in the second sector, wherein an annular damping ring is attached to an outer peripheral portion of the bellows cap such that the bellows body and the bellows cap do not directly contact against an inner wall surface of the shell, an outer peripheral surface of the damping ring and the inner wall surface of the shell are slightly spaced in a radial direction and can smoothly slide without impeding expansion and contraction of the bellows, wherein the loose end of the bellows body is slightly spaced in the radial direction from the outer peripheral surface of the damping ring and the inner wall surface of the shell, and as a result when the accumulator receives external vibration, the outer peripheral surface and the inner wall surface repeat abutment while slightly vibrating in the radial direction within the vibrating shell.