Electric motor and electric power steering device using the same

An electric motor comprising;

• a rotation shaft;
• a rotor mounted to the rotation shaft;
• a stator mounted so as to oppose an outer peripheral surface of the rotor;
• a cylindrical holder mounted to an end of the rotation shaft;
• a sensor magnet mounted to the holder;
• and
• a rotation sensor mounted at a position at which the rotation sensor opposes the sensor magnet in a direction of an axis of rotation and detecting a rotating field of the sensor magnet;
• wherein
• the end of the rotation shaft where the holder is mounted has a cylindrical shape with a non-circular cross section formed of at least one plane and a curved surface in an outer peripheral portion;
• at least one of an inner peripheral portion and an outer peripheral portion of the holder forms a non-circular cross section formed of a plane parallel to the axis of rotation and a curved surface connected to the plane;
• the plane of the rotation shaft and the plane of the holder are parallel to each other and the curved surface of the rotation shaft and the curved surface of the holder are in contact with each other;
• and
• the sensor magnet is integrally molded with the holder continuously from an inside of the holder to an outside of the holder through a hole provided on an end face of the holder.