PURPOSE: To prevent fluid from being leaked from an excision surface and improve pump efficiency by introducing the exhaust fluid to a gap between a reverse part of the excision surfaces in which a pair of metal peripheries are excised to each other and press-welding a pair of metals to each other.

CONSTITUTION: A pair of metals 5 and 6 form each cylindrical peripheral surface and a part of these peripheries are excised by the surface which is parallel to an axial center. Those excision surfaces 9 and 10 are made contact to each other and fit in the metal fitting holes 12 and 13 of a casing 11. Gears 1 and 2 revolve toward an arrow and fluid is sent to an exhaust outlet 15 from a suction inlet 14. Gaps 5 and 6 are provided between the reverse parts 18a and 19a of the excision surfaces 9 and 10 for the peripheries 18 and 19 of the metals 5 and 6 and the walls for the metal fitting holes 12 and 13 of the casing 11. By making the discharge fluid flow in these gaps 16 and 17, the metals 5 and 6 are pushed to each other and the fluid is prevented from being leaked from the excision surfaces 9 and 10.