PURPOSE: To efficiently and neatly color a concavity in a various types of sheet facing materials, by a method wherein a thermoplastic coloring film is placed in correspondence to a position where a concavity is formed by the use of said film, and the film is fused and secured at the same time when a welding process is made on the concavity.

CONSTITUTION: In case a welding process is made on a surface of a facing material, in which a foam material 1 is covered by a surface film 2 and a lining film 3, to form a concavity 4 in the shape of quilting, beeline, circular button, a coloring film 6 is placed corresponding to a position allowing the concavity 4 to be formed. Said film 6, made of thermoplastic resin such as polyvinyl chloride, can be welded by heat when it is pressed by a high-frequency electrode or a heating mold 5. Or, when the concavity 4 is formed, the film 6, simultaneously, is welded by heat, and this allows to perform an easy coloring.