PURPOSE: To make it possible to increase the heat exchange efficiency and to reduce the space cooling and heating loads by providing the device with a thermoelectric plate pinched by surface plates, exhaust side fins provided in an exhaust passage, supply side fins provided in an air supply passage, and means for switching the current flowing direction of the thermoelectric element.

CONSTITUTION: In summer season, the inside of the room is cooled, and external warm air introduced from a feed air inlet 18 into a duct case 14 makes contact with feed air side fins 58 by a thermoelectric plate 42, being robbed of its heat and cooled and fed as fresh air having a temperature which is equal to the room temperature. On the other hand, thermal energy imparted to feed air side fins 58 is transmitted to the surface plate on the exhaust side, and increased by the thermoelectric element to warm an exhaust side fins through other surface plate. Indoor air which has been introduced from the inside of the room into an exhaust duct case 16 makes contact with the exhaust side fins, robbing the exhaust side fins of heat and discharged out of the room. On the other hand, when the inside of the room is heated in winter season, a current flowing to the thermoelectric element is caused to flow in a manner reverse to the above described case, whereby the thermal energy of the exhaust air is drawn up by the thermoelectric plate through the surface plate, and is transmitted to the feed air. The feed air which is allowed to have a temperature which is equal to the room temperature is introduced into the room.