PURPOSE: To prevent lowering of the heat exchange efficiency of a heat exchanger and reduc tion of a ventilating flow rate by a method wherein a heat pipe type heat exchanger is mounted astride a space between a discharge passage and a feed passage, the part on the discharge passage side of the heat exchanger is situated to a suction port on the indoor side, and a filter is arranged in a state to be adhered to a part on the discharge passage side.

CONSTITUTION: A heat pipe type heat exchanger 14 extending through a partition plate 8 and mounted astride a space between a discharge passage 4 and a feed passage 7 has a part 15 on the discharge passage side at a suction port 2 on the indoor side, and filters 16 is mounted in a state to be adhered to the part 15 on the discharge passage side of the heat pipe type heat exchanger 14. Outdoor air is sucked through a suction port 5 on the outdoor side and fed to the interior of a room through a discharge port 6 on the indoor side after the passage of it through the feed passage 7 and a part 17 on the feed passage side of the heat pipe type heat exchanger 14. The outdoor air can be heat-exchanged and ventilated through the heat pipe type heat exchanger 14. During a winter season, the part 17 on the feed passage side of the heat exchanger 14 is cooled by means of outdoor air, the surface temperatures of the part 15 on the discharge passage side and the filter 16 are reduced, and the temperature of soot passing through the filter 16 is lowered to improve the collection efficiency of the filter 16.