Abstract: A motor addresses the problem of a decrease in usability due to the use of a complex structure on a counterpart mechanism on which the motor is mounted, the complex structure being used to prevent rotation of the motor on the counterpart mechanism while centering the motor shaft. The motor includes: a rotor with a shaft; a housing covering an outer periphery of the rotor; and an end plate covering an end portion of the housing in an axial direction of the rotor. The end plate includes a protruding portion for enabling external contact protruding in a direction in which the shaft extends. The protruding portion has an outer peripheral surface having a non-circular shape in a cross section perpendicular to the direction in which the shaft extends, and has an opening through a face thereof opposing the shaft.