PURPOSE: To provide a motor driven pump which can enhance the sealing performance of a cooling water circulating channel system while having its reliability enhanced.

CONSTITUTION: A motor frame 2 is provided with a water running port 29 penetrating in its cylindrical direction, and a counter-load side bracket 5 is provided with a communicating passage 30 for communicating the water running port 29 with a rotor chamber 28. In addition, a load side bracket 13 is provided with an outlet passage 32 for communicating the water running port 29 with the pump section side, and also an inlet passage 31 is provided, for communicating the discharge side of a pump chamber 26 with the rotor chamber 28.