A shaft secured to a hub is inserted and rotatably supported in a sleeve secured to a base. A dynamic pressure groove is formed in the inner peripheral surface of the sleeve, and lubricant is sealed between the shaft and the sleeve. The rotation of the shaft causes dynamic pressure to generate in the lubricant due to the dynamic pressure groove, supporting the shaft floatingly. The crystallized-glass sleeve allows heat generated in a coil to be hardly transferred to the shaft, thereby reducing the variations in the clearance between the shaft and the sleeve due to temperature changes to a minimum in cooperation with the crystallized-glass sleeve with a low thermal expansion coefficient. Finishing accuracy of the bearing surface can be improved by chemical polishing. Consequently, the rotation accuracy can be improved and the leakage of lubricant due to the variations in the clearance can be prevented.