PURPOSE: To make it possible to ventilate a room without impairing the indoor space heating effect by heating indoor air by a heater, circulating a part of air within a room, and exchanging heat of a part of remaining indoor air with outdoor air by the heat exchanger to discharge the former.

CONSTITUTION: A blower 2 is actuated and power is supplied to a heater 7, and a second discharge port 4 is closed by a damper 8. Air sucked up from a first suction port 5 by the blower 2 under this condition is heated by a heater 7 together with air sucked up through an outside suction port 6, and is discharged to a bathroom a through a first discharge port 3. Since the inside of the bathroom A is put into a positive pressure, a part of air passes a heat exchanger 10 and is discharged to the outdoors I through an outdoor discharge port 9. When air sucked up through the heat exchanger 10 passes through the heat exchanger 10, it is subjected to a heat exchange with air discharged, and heat within discharged air is recovered into the bathroom A through the blower 2. By these procedures, the wasteful use of heat energy is reduced and thus the ventilation can be made without impairing the space heating effect.