To integrally form a car body attaching part and an attaching screw holder by forming a slit serving also as a screw inserting port by the main body part of a metallic mold in a side wall surface whose outer surface comes into contact with the slide surface of the attaching screw holder.

A main body part 30 includes an insertion port forming part 31 formed to be protruded and roughly T-shaped in section by a head part 32, a leg part 33 and a slit part 34. A roughly T-shaped fitting part 43 is provided in a hollow part forming part 42 as a part of a carved-in part 41 provided in a slide metallic mold 40 side and during molding the tip of the insertion port forming part 31 is engaged with the fitting part 43. Even if a metallic mold removing direction X for forming a car body attaching part 11 provided in, for instance the housing of a vehicular lamp 10 is different from an attaching screw inserting direction, the attaching screw holder is integrally formed in the car body attaching part 11.