A humidifying device has an adsorption module and a blower. The adsorption module has the adsorbent. The adsorption module is configured to adsorb the water from the air passing through the adsorption module to the adsorbent and is configured to desorb the water from the adsorbent to air passing through the adsorption module. The blower blows the air to the adsorption module. The blower, in an adsorption operation in which the adsorbent adsorbs the water from air, draws the air from a roof space and blows the air to the adsorption module whereby the adsorption module adsorbs the water from the air. The roof space is defined between a vehicle ceiling panel and a ceiling interior member.