PURPOSE: To enable work on the installation of a pump to be carried out easily by providing an installation support leg on the bearing bracket of a motor and by mounting a pump casing with a pump room on the side surface of said bearing bracket in such a manner that its circumferential position is changeable.

CONSTITUTION: On the lower end of the bearing bracket 30 of a drive motor 21, an installation support leg 28 is provided, while, on the side surface of said bearing bracket 30, a pump casing 24, comprising a cover 26, a port plate 25 and an air-intake passage 32, is mounted by the use of a bolt 36 in such a manner that its circumferential position is changeable, and it is concentrical with the rotating shaft 22 of the motor 21. Thereby, the positioning relation between the installation support leg 28 and the pump casing 24 to be connected to a piping is adjustable such that the pump installation work can be carried out more easily.