To reconcile the enhancement of productivity and the lowering of a waste article generation ratio.

A projection 48 formed into an almost inverted L-shape in its cross section and having sharpened leading end 48B' is provided to a skin mold 46 along a tear line and a predetermined stepped part 54 is formed thereto. When this skin mold 46 is used to perform powder slush molding, a skin overlap part 44 having the same shape as the projection 48 is formed and separated simultaneously with demolding. Next, the skin 38 on a door side is displaced toward the skin 30 on a panel side 30 by stepped quantity to bring the skin terminal part 44 on a door side into close contact with the skin terminal part 30 on an in-panel side. By this constitution, a close contact flange becomes long. Therefore, even if urethane penetrates from the separation part of the skin overlap part 44 at the time of subsequent foam molding, it can be interrupted on the way to be prevented from leakage.