PURPOSE: To prevent the inflow of a molten resin to the rear surface of an inlay material and the outflow thereof at the time of clamping by providing the projection piece directed toward the bottom surface of a male mold to the outer peripheral edge part of the inlay material and inlaying the projection piece in the bottom surface of a female mold to support the same and engaging the projection piece by a double engaging member to fix the inlay material to the female mold.

CONSTITUTION: An inlay material 1 made of vulcanized rubber is prepared and a projection piece 2 is integrally provided to the outer peripheral edge of the inlay material 1 so as to be directed toward the bottom surface 4 of a female mold 3 while double engaging members 5, 5' holding the projection piece 2 from both sides thereof are integrally erected on the bottom surface of the female mold 3. The projection piece 2 of the inlay material 1 is inserted and inlaid in the groove formed by the double engaging members 5, 5' to be fixed. In this state, a male mold 6 and the female mold 3 are clamped and molten polyurethane is injected into the cavity 7 formed by both molds.