PURPOSE: To minimize the useless expense, as well as to reduce the time to reach to the temperature to allow the printing, by controlling the rotation of a fan motor corresponding to the temperature detected by a detecting means which detects the temperature of a heat fixing unit.

CONSTITUTION: As a heat source in the fixation time, a halogen heater 9 provided in a fixing roller is used. A thermistor 7 is installed on the surface of the fixing roller, and it detects the temperature of the fixing roller. This thermistor 7 is connected in series with a resistance 8, and its partial pressure value is taken in to an A/D board of a one chip MPU furnishing the A/D converter of a CPU 3. The CPU 3 detects the temperature of the fixing roller by a temperature signal, takes on and off a power feeding control signal from an output port, controls the lighting of the halogen heater 9, and controls the temperature of a fixing unit 10. In this case, the operations of fan motors 4 to 6 are controlled to stop or to rotate at a half speed, corresponding to the variation of the temperature of the fixing unit 10, until the fixing unit 10 reaches to a specific temperature.