PURPOSE: To remarkably reduce noise with a simple constitution and facilitate waste disposal by forming a bolt inserting hole into a polygon, and press-fitting a washer having a diameter larger than a side of the bolt inserting hole after insertion of a bolt or a nut.

CONSTITUTION: A pump unit having an electric motor 2 is mounted on a pump base 1 made of a synthetic resin, where an intake water passage 9, a discharge water passage 21, an a tunnel-like hole 28 for outside wiring are formed. A sealed type pump cover not having a cut portion is supported in such a manner as to cover the pump unit. A bolt inserting hole 42 is formed for fixing the electric motor 2 to the pump base 1 made of a synthetic resin. The bolt inserting hole 42 is formed into a polygon. A washer 43 having a diameter larger than a side of the bolt inserting hole 42 is press-fitted into the bolt inserting hole 42 after insertion of a bolt 41 or a nut 44. Consequently, it is possible to take productivity, installation performance and discard into consideration, and to reduce noise and enhance safety.