PURPOSE: To miniaturize the device, reduce pressure loss by shortening the lengthes of air discharging and sucking paths and improve the assembling property of the device by a method wherein an air discharging fan and an air suction fan are arranged in the upper of an outer casing by attaching these fans to one rotating shaft of a motor while a heat exchanger is arranged in the lower part of the outer casing.

CONSTITUTION: The air discharging fan 19, sucking indoor air and supplying the air to the air discharging part of the heat exchanger 18, and the air suction fan 20, sucking outdoor and and supplying the air to the air suction path of the heat exchanger, are arranged in the orthogonal direction to an outer wall 21 and are attached coaxially to one rotating shaft 23 of the motor 22. The contaminated air in a room is sucked from the air discharging grille 27 of the outer casing 24 and is guided to the air discharging path of the heat exchanger 18 along an air discharging casing 33 by the rotations of the air discharging fan 19 and the air suction fan 20. The fresh outdoor air is sucked from a weather cover 34 and is guided to the air suction path of the heat exchanger 18 along an air sucking casing 30.