PURPOSE: To enable a shaft to be rotated and moved in the axial direction, by moving a rotor and the shaft fixed on the rotor, with an electromagnet in the axial direction, to stop them at a given position, and by rotating the shaft at the position.

CONSTITUTION: When a motor or the like is driven and a pulley 10 is rotated via a timing belt or the like, a shaft 5 is also rotated. If a switch 14 is not turned ON, a rotor 6 and the shaft 5 are rotated at a position determined by a spring 11. When the switch 14 is turned ON, then a current flows to a coil 8, and the iron piece 7 of the rotor 6 is attracted. Accordingly, the rotor 6 and the shaft 5 are moved on the right resisting the force of the spring 11, and a thrust bearing 12 is stopped being abutted against a step 15 set on a housing 2, and at the position, the shaft 5 and the rotor 6 are rotated.