PURPOSE: To make it possible to produce high starting torque under low temperature by previously setting starting voltages corresponding to a plurality of temperature zones, detecting the ambient temperature at the time of starting, and then determining a starting voltage corresponding to the ambient temperature.

CONSTITUTION: A fan motor 1 is provided with a motor driving section 2, a control section 3, and a temperature sensor 4. The control section 3 receives pluses from a Hall element mounted on the fan motor 1 in order to detect the number of revolution and produces trigger pulses for performing phase control of a triac 6 in the motor driving section 2. A plurality of split temperature zones and starting voltages of the fan motor 1 corresponding to the temperature zones are previously set in the control section 3. At the time of starting the fan motor 1, the temperature sensor 4 detects the ambient temperature of the fan motor 1 and decide the starting voltage judging to which of temperature zone belongs. According to the constitution, high starting torque can be obtained even under low temperature.