A gear pump (1) that discharges a fluid by rotating while a pair of gears (11, 12) are intermeshed includes a body (2) into which the respective gears (11, 12) are incorporated, a housing (3, 4) that contacts the body (2), a number of particles (30) that are interposed between an end surface (25, 26) of the body (2) and an end surface (28, 29) of the housing (3, 4), which contact each other, to prevent positional deviation between the body (2) and the housing (3, 4), and a fastening member (17 to 20) that fastens the housing (3, 4) to the body (2).