To prevent any rust from taking place in the jointing part of a shell to deteriorate its fixing attachment by forming a deformed part on the spirally fitting surface of the screw part between a cylinder and an end cover.

An accumulator 1 is composed of a shell 2 in whose inner peripheral surface 15 a hollow chamber 3 is formed and a piston 6 fitted freely slidably on the inner peripheral surface 15. This shell 2 is constituted in such a way that an end cover 11 in which the second screw part 12 is provided is screw jointed to the first screw part 10 formed on the external peripheral surface 9 of the opening part 8 of a cylinder 7 having its bottom and cylindrical shape. And also, the shell 2 is subjected to such surface treatment as plating, etc., so as to fit the piston 6 in the cylinder 7 and additionally the second screw part 12 of the end cover 11 is tightened to the first screw part 10 of the cylinder 7 up to its terminal end while making screw jointing the second screw part 12 of the end cover 11 to the first screw part 10 of the cylinder 7. Next, a thin wall part 13 is given hit scars by means of a chisel, a deformed part 17 is formed on mutually screwed surface 14 so as to engagingly lock the cylinder 7 to the end cover 11. Since this hit scar is formed in a small size, plating may not be peeled off at the time of making hit scars.