PURPOSE: To prevent discharge of volatile component of adhesive for fixing a magnet to a yoke.

CONSTITUTION: A stator 2 is mounted on a bracket 1, a hub 6 is fixed to a shaft 5 to be supported by a bearing 4, and a cylindrical magnet 8 is fixed to a cylindrical yoke 17 mounted on the hub 6 with adhesive. A flange 17a directed inside is formed at the yoke 17, brought into contact with the magnet 8, and an annular groove 17b is formed at the periphery of the flange 17a. When the inner periphery of the yoke 17 is coated with a suitable amount of adhesive and the magnet 8 is press-fitted, a slightly excess adhesive is scraped by a corner of the magnet 8 to be retained in the groove 17b. The magnet 8 is brought into axial contact with the flange 17a to seal the slightly excess adhesive in the groove 17b.