An air-conditioning system includes at least one outdoor unit including a compressor, a four-way valve, and an outdoor heat exchanger, at least one indoor unit including an indoor unit expansion valve and an indoor unit heat exchanger, and at least one humidity control device including a humidity control device expansion valve, a humidity control device heat exchanger, and first and second water adsorption/desorption devices. The compressor, the four-way valve, the outdoor heat exchanger, the indoor unit expansion valve, the indoor unit heat exchanger, the humidity control device expansion valve, and the humidity control device heat exchanger are connected to each other with pipes so as to constitute a refrigerant circuit.