To provide an efficient motor pump capable of minimizing input power even in the rotation of an impeller at high speed in water.

This motor pump comprises a housing case having a connecting passage arranged between a first cap and a second cap to connect a passage intake port to a passage delivery port and forming a stator, and a rotor having a rotating shaft rotatably arranged within the housing case. A diagonal flow impeller 60 for running a fluid from the passage intake port to the passage delivery port is arranged in a part of the rotating shaft of the rotor. On the surfaces of the diagonal flow blades 62a-62d of the impeller 60, grooves 63 (63a-63e) are provided in positions set so that the fluid feed quantity of the diagonal flow impeller 60 is constant between the outer side and the inner side.