To introduce fresh air into a room by favorably reducing an effect of dew condensation.

Dew condensation occurs when outside air passes a water collection chamber 20, a heat exchange pipe 18, and a passage 14, and it contains moisture, and waterdrops 40 adheres to wall surfaces of the water collection chamber 20, the heat exchange pipe 18, the passage 14, or the like. Since the heat exchange pipe 18 is slantly arranged, the waterdrops 40 of the passage 14 and the heat exchange pipe 18 are gathered into the water collection chamber 20. The waterdrops 40 of the water collection chamber 20 or a passage 30 drop down, and they are also gathered into the water collection chamber 20. A driving controller 30 drives a drain pump 22, and water collected in the water collection chamber 20 is drained to a ground surface side.