To relatively position a body, a front cover and a rear cover without using a positioning pin or spigot or the like.

A bolt insertion hole 16 for having a bolt 4 for fastening and joining a body 11, a front cover 12 and a rear cover 13 inserted therein is bored on the body 11, the front cover 12 and the rear cover 13 constructing a housing 1 of a fluid pressure pump or a motor, inner circumference thereof is accurately machined and is made roughly consistent with an outer circumference of a cylinder part 42 of the bolt 4. The body 11, the front cover 12 and the rear cover 13 are relatively positioned by closely arranging the cylinder part 42 of the bolt 4 in the bolt insertion hole 16 without clearance.