Abstract: An evaporator 6 and a condenser 7, which are made of spine fin tubes 19, are arranged in the same vertical plane, so that the evaporator 6 is located at the top, while the condenser 7 is located at the bottom. Water condensed at the evaporator 6 drops onto an outer surface of the condenser 7. The water is moved along all of vertically spaced straight portions of the spine fine tubes 19 constructing the evaporator 7, which are in the same vertical plane. An increased staying time of the water on the evaporator 7 is, thus, obtained, thereby effectively evaporating the drained water due to the heat transferred from the evaporator 7.