Electric drive device and electric power steering device

An electric power steering device comprising:

• an electric motor providing a steering assistive force to a steering shaft on the basis of an output from a torque sensor that detects a turning direction and a turning torque of the steering shaft;
• a motor housing accommodating therein the electric motor;
• a heat radiation base body fixed to an end surface, which is an opposite side to an output shaft portion of a rotation shaft of the electric motor, of the motor housing and extending in a direction of the rotation shaft which is the opposite side to the output shaft portion;
• one electronic control unit of a redundant system, the one electronic control unit arranged along a direction in which the heat radiation base body extends and having a board that is fixed to the heat radiation base body with thermal conduction to the heat radiation base body allowed;
• the other electronic control unit of the redundant system, the other electronic control unit arranged along a direction in which the heat radiation base body extends and having a board that is fixed to the heat radiation base body with thermal conduction to the heat radiation base body allowed;
• and
• a cover covering the heat radiation base body and the one and the other electronic control units and liquid-tightly connected to the end surface of the motor housing at a facing surface of the cover with the end surface of the motor housing without using a bolt.