An axial alignment structure for a fluid pressure pump (100) includes: a first housing made of a resin; and a second housing made of a resin, in which a housing is configured in a state where the first housing and the second housing are joined to each other by thermal welding at a welding position, and a pump rotor is accommodated in the housing, and the first housing and the second housing have an axial alignment mechanism that axially aligns the first housing and the second housing such that axes of the first and second housings coincide with each other at the time of joining of the first housing and the second housing to each other by the thermal welding.