A pair of penetrating holes are formed along a longitudinal direction in the interior of a cylinder body that constitutes a fluid pressure cylinder. One end of the pair of penetrating holes is sealed by a pair of caps formed in plate-like shapes. The caps, for example, are formed by press molding a plate body made up from a metal material such as aluminum or the like. Outer edge portions of the caps include bent portions, which are inclined at a predetermined angle in a radial outward direction. In addition, the caps are installed by means of the bent portions biting into inner circumferential surfaces of the penetrating holes.