To solve such a problem that condensation is hard to occur at a dry place so that water cannot be supplied, when condensing water content at the cooling part of a Peltier element and supplying water, and contrarily, that water is accumulated too much at a high-humidity place so that large droplets are discharged.

Aluminum fiber assembly is fitted at the cooling part of a Peltier element to enlarge the surface area of the cooling part. Thanks to such a structure, condensation is caused to make large droplets be soaked in the aluminum fiber assembly, thereby preventing the large droplets from being discharged.