PURPOSE: To surely start a motor by driving control the heater, which is placed near a bearing, in accordance with the temperature of a fluid bearing and keeping the viscous resistance of the fluid optimum.

CONSTITUTION: When a spindle motor 51 is started, a temperature detector 39 detects the temperature of a radial direction bearing 21 to transfer it to a control means 47 through a temperature detecting circuit 41. The means 47 judges whether the detected temperature of the bearing 21 is below a prescribed temperature or not. If the temperature is below the prescribed temperature, a heater driving circuit 37 is driven, a stator 23 is energized, the bearing 21 is heated and the fluid viscosity is reduced. When the bearing 21 reaches to the prescribed temperature, a motor driving circuit 33 is driven, the stator 23 is energized, a magnetic field is generated and a hub 9 is given a rotational force. If the detection result of the detector 39 is more than the prescribed temperature, the means 47 immediately drives the circuit 33. Thus, the motor 51 is surely started.