To prevent damaging of an interior trim part stored in a tube, without breaking a sealing member arranged in an opening end part of the tube, even if curl processing is performed.

A thin part 20 is formed without generating a step height on an inner surface by reducing an outer diameter of the opening end part of a cylinder 1 of a single cylinder type gas containing hydraulic shock absorber. The required interior trim part is stored and sealed in the cylinder 1 by gas, and after sealing an oil liquid, among the interior trim part, a sealing member including a rod guide 7, an oil seal 8 and a presser plate 18 is temporarily fastened between an inner peripheral projection 16 formed by beading processing and the thin part 20 bent and deformed inside a little, and afterwards, the thin part 20 is bent and deformed inside by the curl processing by a rocking system, and its breaking is prevented by reducing a load applied to the rod guide being a sintered product.