Annular grooves having substantially V-shaped cross sections are formed on the front surface and the rear surface of a grille body. A through hole communicating to the front surface and the rear surface of the grille body is also formed so that the front aperture may be smaller than the rear aperture. A protrusion is formed on the rear surface of the grille body, which is located inner than the groove. The grille body is immersed into a chemical plating solution to form a chemical plating layer on the entire surface of the grille body except for the bottoms of the grooves. The grille body is then subjected to undercoat plating, in which the grille body is immersed into a predetermined plating solution utilizing the protrusion as a kind of electrode so as to electrically charge the chemical plating layer present on the front surface from the layer present on the protrusion and through the layer present in the through hole to allow an undercoat plating layer to be formed on the portions where decorative plating is formed. The chemical plating layer formed on the portions where no decorative plating is formed is dissolved by a predetermined solution. A general electroplating layer is formed likewise on the undercoat plating layer. The chemical plating layer and the electroplating layer are formed only on the to-be-plated portions. The protrusion does not impair the front appearance of the front grille.