Most of the ancient Japanese metal artifacts with gold surface were fabricated from copper or copper alloys. Their surfaces were treated by gilding, especially by fire gilding with gold amalgam for obtaining brilliant appearance. Scanning electron microscope (SEM) observation was done to the sample surfaces made experimentally applying traditional gilding method. On the basis of these results, the surfaces of gilded metal artifacts that were excavated from archaeological sites were characterized. It was revealed that final polishing process is important process for obtaining gold brilliance. The precipitate particles of gold amalgam, which are the most prominent feature of fire gilding, remained on the surface even after the final polishing. The trace of polishing was also recognized on the surface. It was found out that the ancient technique of fire gilding can be detected by these remarks on the surface.