Abstract: An apparatus for recovering fresh water or for concentrating a liquid has a structure formed of a roof member 10 having a gradient and a base member 14 provided with a liquid reservoir member 18. A cellulose-based film 20 has one surface saponified 2 to 50 .mu.m deep and the other surface is attached to the inner surface of the roof member. A liquid recovery member 16 is provided in the roof member or the base member, the liquid recovery member being for recovering water which is condensed on the saponified surface of the cellulose-based film and that flows downward.