Heat exchangers of a refrigerant circuit are constructed of a first adsorption heat exchanger and a second adsorption heat exchanger, both of which have an adsorbent supported thereon, and are constructed so as to be switched into an evaporator and a condenser. An air passage is constructed so as to be switched into states in which air flowing from the outside of a room to the inside of the room and air flowing from the inside of the room to the outside of the room flow through either of the first adsorption heat exchanger and the second adsorption heat exchanger. A dehumidifying operation mode and a humidifying operation mode can be performed by switching the flow of refrigerant and the flow of air at specified intervals, a cooling operation mode and a heating operation mode can be performed without switching the flow of refrigerant and the flow of air, and an ventilating operation mode can be performed by flowing air through the air passage in a state where the refrigerant circuit is stopped.