PURPOSE: To reduce the whole shape and the size of a permanent magnet by clamping the permanent magnet between a yoke projecting along the outside surface of a coil and a side yoke on one end of the coil in its axial direction.

CONSTITUTION: A step is made at a shoulder 12a of a bobbin 12. A permanent magnet 16, which is clamped by the other end of a side yoke 13 and the other end 11b of a yoke 11, is laid out on this step portion. A bobbin 22 is extended to its one end side in the axial direction where a holder 22a is formed. The holder 22a envelops both ends 11a and 11b, the permanent magnet 16, the side yoke 13 and a yoke piece 23 so that they may be positioned. This construction makes it possible to reduce the size of the permanent magnet, and what is more, to minimize the outside dimensions of an actuator, and enhance assembling accuracy and make the most use of generated fluxes as well.