PURPOSE: To shorten the drying time in winter and to prevent the color-changing of synthetic fibre clothes caused by the excessive rise of temperature by controlling the revolutionary speed of a fan-driving motor variably for maintaining the exhaust temperature at the completion of drying essentially in a constant level without regard to the open-air temperature.

CONSTITUTION: When a door is closed and a starting switch 18 is manually closed in the closing state of a door switch 16, a relay coil 17 is excited to close the contact 17a for self-holding, and contacts 17b and 17c are also closed for operating a motor 5 and a heater 10. Since the resistance of a thermistor 50 is changed according to the open-air temperature, the time constant to charge a condenser 51 is change. Consequently, the firing phase of a tri-arc 47 is changed, and the revolutionary speed of the motor 5 is changed into a high speed when the open-air temperature is high, and into a low speed when the open-air temperature is low.