PURPOSE: To effectively cool an electric motor and a pump by forming a space between the pump with which a revolution shaft is connected and the electric motor and forming a hole for the communication between the space and the inside of the electric motor and allowing a fan fixed onto the electric motor shaft to revolve in the space.

CONSTITUTION: The revolution shaft 6 of a pump 1 is connected with the shaft 7 of an electric motor 2 through the space 5 formed by the bracket 3 of the electric motor 2 and the side plate 4 of the pump 1. Further, a hole 9 for the communication between the space 5 and the inside of the electric motor 2 is formed onto the bracket 3. When the electric motor 2 revolves, a fan 8 installed onto the shaft 6 stirs the air in the space 5, and said air flows into the inside of the electric motor 2 through the communication hole 9. Therefore, the air circulates inside the electric motor 2 and the inside the space 5, and cools the electric motor 2 and the pump 1. Therefore, the inflow of air from outside is prevented, and transport of foreign materials into the cooling air is prevented, and effective cooling is permitted.