In an adsorption operation in which the adsorption agent adsorbs water, air in a vehicle compartment flows into an adsorption agent module after being cooled by passing around a heat sink. On the other hand, in a desorption operation in which the water is desorbed from the adsorption agent, the air in the vehicle compartment flows into the adsorption agent module to be humidified without being heated or cooled, and humidified air is cooled by passing around the heat sink and blown into the vehicle compartment. Accordingly, a temperature of the humidified air can be prevented from increasing unnecessarily by a simple configuration with which the air in the vehicle compartment is cooled in the heat sink.