PURPOSE: To reduce the pressure loss of an air current and to improve the heat exchange efficiency by installing a blower for a primary air current and that for a secondary air current each having a thickness less than the length of a short side of each end surface, on both end surfaces in the direction of an air current passage of a counter-flow type exchanger.

CONSTITUTION: Primary air currents A sent by blowers 3 for supplying primary air currents flow into the heat exchanger through a primary air current inlet ports 5 of a counter-flow type heat exchanger 2 and is discharged out of a primary current discharge outlet 7, and secondary air currents B sent into the heat exchanger by secondary air current supplying blowers 4 flow into the heat exchanger through a secondary air current inlet part 6 and is discharged through a secondary air current discharge port 8. The primary air current A and secondary air current B undergo heat exchange within the counter-flow type heat exchanger 2 through a partition plate 10. Each of heat exchangers 3 and 4 for supplying respective air currents having a dimension which is equal to or shorter than a shortest side 11 of the counter-flow type heat exchanger 2 are installed on the surfaces of inlet ports of respective air currents of the counter-flow type heat exchanger 2, whereby it is possible to supply respective air currents uniformly over the entire part inlets 5 and 6 of respective air currents. Therefore, the lowering of the heat exchange efficiency is prevented and the pressure loss of respective air currents can be reduced.