PURPOSE: To improve an air stream into a humidifier, and to efficiently effect humidification by positioning the air inlet port of the humidifier above the outlet port of a blower for air feed.

CONSTITUTION: The air inlet port 17 of a humidifier 14 is positioned in the downstream of the outlet port 16 of a blower 13 for air feed. Outdoor air is sucked in by the blower 13 for air feed through an outdoor side inlet port 4 and, after passing through a neutral filter 12 and being subjected to heat- exchanging by a heat exchanger 7, the outdoor air is humidified on the lower side of the humidifier 14 and also by the humidifier 14, passes through a drain filter 15 and is then sucked into a room through an indoor side outlet port 3. On the other hand, indoor air is sucked in by a blower 10 for exhaust through an indoor side inlet port 2 and is exhausted outside the room through an outdoor side outlet port 5 after passing through a filter 9 for coarse dust and the heat exchanger 7. Accordingly, air blown by the blower 13 for air feed does not directly impinge against the air inlet port 17 of the humidifier 14 and can be slowed down to a necessary air speed. Further, air is less involved into a spray outlet port 19, and the spray generated can effectively be induced, thereby enabling the air to be humidified efficiently.