PURPOSE: To reduce energy loss generated by circulating and utilizing regerated air by means of a heat pump system, eliminating a duct to introduce regenerate air into and out of a room, and reusing the heat of regenerated air.

CONSTITUTION: A dehumidifying device A is placed in a room to be dehumidified, and air in the room is dehumidified in an inner air passage 1 by rotating continuously a dehumidifying rotor 4 constituted with an active carbon sheet impregnated with lithium chloride formed up in a shape of one-side corrugated cardboard and wound up in the form of a roll. On the other hand, the regenerated air heated up by a condenser 9 of a heat pump system 7 is passed through a generated air passage 2, and water vapor is discharged out of a dehumidifying rotor 4. Moisture adsorbed regenerated air is cooled down in a regenerated air chamber 6 by an evaporator 11, and after drain is separated, the regenerated air is heated by the condenser 9 again, returned into the regenerated air passage 2 and circulated in the passage.