PURPOSE: To enable to utilize a bathroom as a drying chamber, by connecting a bathroom to a returnable duct to introduce the air for air-conditioning by a returnable air passage provided with dampers, which are constituted to be selectively changeable, in an air-conditioning system having air-warming, air-cooling and air-dehumidifying functions.

CONSTITUTION: When an air intake and an air discharge ports 29 (not shown in fig) and 30 (not shown) for the air to and from a bathroom are closed by dampers 31 and 32 which partition off the bathroom 2 from the air passage, an intake and a discharge ports 27 and 28 for the air for air-conditioning are opened, and the air from a living room is transmitted into a heat exchanging chamber to be conditioned and dehumidified. To the contrary, when the intake and the discharge ports 29 and 30 for the air to and from the bathroom are opened by the dampers 31 and 32, the intake and the discharge ports 27 and 28 for the air for air-conditioning are closed, and the air in the bathroom 2 is fed into the heat exchanger chamber 25 for air conditioning, heat-exchanging and dehumidifying and then is returned to the bathroom 2. With such a constitution, the bathroom can be utilized as a drying chamber without providing any other particular drying facilities separately.