To prevent water droplets that form on the indoor ceiling surface of a bathroom from dropping so as to provide increased bathing comfort by using a hydrophobic material to form at least the surface layer of a ceiling member facing the indoor side of a bathroom, and roughening the surface of the surface layer.

A surface layer 6 of a hydrophobic material is used to form at least those surfaces 3a, 5a of panel members 3, 5 which face the inside of a bathroom, the panel members 3, 5 being a ceiling member and a lid panel member of the inner ceiling surface of the bathroom, respectively. In this case, water that precipitates if steam pressure within the bathroom being used becomes oversaturated condenses into droplets on the inner ceiling surface of the bathroom. Water produced by cooling and condensing of steam from a steam sauna device condenses into fine, independent droplets clinging to the ceiling surface, thus making the ceiling surface unlikely to be wetted and making water unlikely to flow down along the direction of inclination of the ceiling surface. Moreover, the water droplets coupled together keep independent of one another and are therefore unlikely to fall. Thus the surfaces 6a of the panel members 3, 5 are roughened 7 into a granular pattern to make the ceiling surface unlikely to be wetted, making it possible to keep the water droplets from falling.