To provide a motor which prevents a shift between an electric angle position detected by a rotation angle sensor and an output shaft position even if a magnetic clutch mechanism operates to cause a slide between its input and output, and enables accurate detection of the position of an object to be driven by an output shaft even if the rotation angle sensor is located closer to the input side of the mechanism.

The pair number of poles of the magnetic clutch mechanism 19 (magnetic attraction units 19a, 19b) is set identical with the number of axial angles of the rotation angle sensor 18 (the number of electric angle cycles per rotation by a rotor 14). As a result, even if relative rotation (slide) occurs at the magnetic clutch mechanism 19, each of the magnetic attraction units 19a, 19b always takes a position shifted to the original position by one cycle of an electric angle of the rotor 14, following reattraction.