According to a humidity controller (10), a first heat exchanger chamber (37) and a second heat exchanger chamber (38) are arranged next to each other in the left-to-right direction in the casing (11). A first adsorption heat exchanger (51) is accommodated in the first heat exchanger chamber (37), and a second adsorption heat exchanger (52) is accommodated in the second heat exchanger chamber (38). The humidity controller (10) alternately performs an operation in which outdoor air passes through the first adsorption heat exchanger (51) and room air passes through the second adsorption heat exchanger (52), and an operation in which outdoor air passes through the second adsorption heat exchanger (52) and room air passes through the first adsorption heat exchanger (51). In the humidity controller (10), dampers (45, 47) which face the first heat exchanger chamber (37) near a supply fan (26), are positioned at locations close to the second heat exchanger chamber (38), and dampers (46, 48) which face the second heat exchanger chamber (38) near an exhaust fan (25), are positioned at locations close to the first heat exchanger chamber (37). This structure reduces a difference between pressure losses of the air in the casing (11) during the respective operations.