PURPOSE: To improve the appearance design and weatherability as an armoring material by spreading a kneaded mixture composed of aggregate and adhesive from above a mosaic pattern frame formed on a fireproof base material and curing this mixture, then removing the frame.

CONSTITUTION: A base plate 1 comprising an incombustible material subjected to a fireproof treatment and/or waterproof treatment is prepd. The kneaded mixture 2' contg. the refractory material for buildings consisting of the fine- grained aggregate, the adhesive, etc., is prepd. Next, the mosaic pattern frame 3 is placed on this base plate 1 and the kneaded mixture 2' is spread thereon from above and is packed into the frame. After the mixture is cured, the frame 3 is removed, by which a surface layer material is formed. This surface layer material is integrally formed with a plural number of molded sections arranged in a mosaic form on its surface part.