To provide a dehumidifying device high in dehumidifying capacity.

An adsoptive element 1 having two flow passages and also having a humidity adsorbent at the inner surface of one side flow passage is provided, and at a dehumidifying stage of the air to be dehumidified, the cooling air for vaporizing the water left in the other side flow passage 3 is made to flow while flowing the air to be dehumidified to the one side flow passage 2 of the adsoptive element 1, and at a desorption stage of humidity adsorbent, high temp. fluid is made to flow in the other side flow passage 3 of the adsoptive element 1 so as to remain the water in the flow passage 3, and at the adsorption stage, the adsorption heat generated at the one side flow passage 2 is removed by vaporizing the water left the other side flow passage 3.