PURPOSE: To dissolve troubles in the opening of a suction port while insuring movement of an impeller in the thrust direction by additionally providing a supporting part to support the center of the impeller capably of being thrusted in the axial direction of a motor on the pump chamber side of a separating plate arranged between the pump chamber and a motor supporting part.

CONSTITUTION: An upper case 4 provided with a separating plate 3 and a suction port 4A is fitted on a fitting plate 1 on which a direct current motor 2 is attached. A magnet case 8 receiving a magnet MG is mounted between the fitting plate 1 and the separating plate 3. Further, a pump chamber 9 is formed within the upper case 4. Meanwhile, a magnet MG is arranged in the position opposite to the magnet case 8 in an impeller case 11 to which an impeller 10 is fitted. In this case, a shaft part 3J having its extreme end rounded is projectingly provided on the pump chamber 9 side of the axial part of the separating plate 3. The shaft part 3J is fitted into the recessed part 11U formed in the impeller case 11, and the impeller case is supported with the shaft part 3J rotatably and slidably in the thrust direction.