An air-conditioning system comprising: at least one outdoor unit (10a, 10b) including a compressor, a flow switching device, and an outdoor heat exchanger; at least one indoor unit including a first expansion device and a first indoor heat exchanger; and at least one humidity control device including a second expansion device, a second indoor heat exchanger, and first and second water adsorption/desorption devices (33a, 33b), characterized in that the compressor, the flow switching device, the outdoor heat exchanger, the first expansion device, the first indoor heat exchanger, the second expansion device, and the second indoor heat exchanger connected in parallel with the first indoor heat exchanger are connected to each other with pipes so as to constitute a refrigerant circuit, wherein, in the humidity control device, the first and second water adsorption/desorption devices (33a, 33b) are disposed in an air path providing communication between an air inlet through which air flows in from a humidity controlled space and an air outlet through which air flows out into the humidity controlled space, the first and second water adsorption/desorption devices (33a, 33b) each including an adsorbent whose equilibrium adsorption capacity with respect to air having a relative humidity in a range of 40% through 100% increase substantially linearly with an increase in the relative humidity, the first and second water adsorption/desorption devices (33a, 33b) being configured to release water into air having a relatively low humidity and adsorb water from air having a relatively high humidity, the second indoor heat exchanger is disposed between the first water adsorption/desorption device and the second water adsorption/desorption device in the air path, and wherein the humidity control device further includes a switching device that switches between a channel in which the air that has flowed in through the air inlet is caused to pass through the first water adsorption/desorption device, the second indoor heat exchanger, and the second water adsorption/desorption device in this order, and a channel in which the air that has flowed in through the air inlet is caused to pass through the second water adsorption/desorption device, the second indoor heat exchanger, and the first water adsorption/desorption device in this order. at least one outdoor unit (10a, 10b) including a compressor, a flow switching device, and an outdoor heat exchanger; at least one indoor unit including a first expansion device and a first indoor heat exchanger; and at least one humidity control device including a second expansion device, a second indoor heat exchanger, and first and second water adsorption/desorption devices (33a, 33b), characterized in that the compressor, the flow switching device, the outdoor heat exchanger, the first expansion device, the first indoor heat exchanger, the second expansion device, and the second indoor heat exchanger connected in parallel with the first indoor heat exchanger are connected to each other with pipes so as to constitute a refrigerant circuit, wherein, in the humidity control device, the first and second water adsorption/desorption devices (33a, 33b) are disposed in an air path providing communication between an air inlet through which air flows in from a humidity controlled space and an air outlet through which air flows out into the humidity controlled space, the first and second water adsorption/desorption devices (33a, 33b) each including an adsorbent whose equilibrium adsorption capacity with respect to air having a relative humidity in a range of 40% through 100% increase substantially linearly with an increase in the relative humidity, the first and second water adsorption/desorption devices (33a, 33b) being configured to release water into air having a relatively low humidity and adsorb water from air having a relatively high humidity, the second indoor heat exchanger is disposed between the first water adsorption/desorption device and the second water adsorption/desorption device in the air path, and wherein the humidity control device further includes a switching device that switches between a channel in which the air that has flowed in through the air inlet is caused to pass through the first water adsorption/desorption device, the second indoor heat exchanger, and the second water adsorption/desorption device in this order, and a channel in which the air that has flowed in through the air inlet is caused to pass through the second water adsorption/desorption device, the second indoor heat exchanger, and the first water adsorption/desorption device in this order.