PURPOSE: To prevent the rotation disabling at the time of a low temperature and to reduce fluctuation amount in torque in a working temperature range in a spindle motor using a dynamic pressure bearing.

CONSTITUTION: A temperature sensor 9 and a heater 6 operating by the sensor 9 are disposed in the vicinity of the dynamic pressure bearing. Then, the temperature of a lubricant 8 for the dynamic pressure bearing is raised at the time of a low temperature. In such a manner, the increase of the viscosity of the lubricant 8 is prevented, thereby preventing the rotation disabling of a shaft 1 and reducing the fluctuation amount in torque, as well.