On inner wall surfaces of a head cover and a rod cover of a fluid pressure cylinder, respective pluralities of first and second spigot pins are installed to project out from the inner wall surfaces. The first and second spigot pins are disposed on circumferences of a predetermined diameter that internally contact or inscribe the cylinder tube. Further, when the cylinder tube is assembled with respect to the head cover and the rod cover, by the flange members of the first and second spigot pins inscribing the inner circumferential surface thereof, the cylinder tube is positioned and assembled coaxially with respect to the centers of the head cover and the rod cover.