A ventilation device includes an outside air heat exchanger disposed between a total heat exchanger and an outside air port, a return air heat exchanger disposed between the total heat exchanger and a return air port, and a supply air heat exchanger disposed between the total heat exchanger and a supply air port. A compressor, a flow switching device, the outside air heat exchanger, an outside air expansion device, and the return air heat exchanger are sequentially connected by pipes, the supply air heat exchanger and a supply air expansion device which are connected in series by pipes are connected in parallel to the outside air heat exchanger and the outside air expansion device by pipes, thereby forming a refrigerant circuit in which refrigerant is circulated.