PURPOSE: To shorten the molding time for a molding of a foamed resin and to adhere firmly a core section to an outer shell section, by separately carrying out a step of molding a core section of a foamable synthetic resin so that it may have a plurality of holes or recessed parts at least in the outer surface and a step of molding an outer shell section.

CONSTITUTION: When a core section 8 of a foamed resin is molded, it is foamed in a heated mold and a plurality of holes or recessed parts 8a are formed at least in the outer surface, while when an outer shell section 9 is molded, a foamable synthetic resin is injected into a cold mold followed by foaming so that foaming at the outer surface 6 is suppressed to form a non-foamed skin layer. The core section 8 and the outer shell section 9 are engaged and a resin is allowed to enter the holes or recessed parts 8a formed in the outer surface of the core section 8 so that they may be adhered firmly. Thus by carrying out the steps of molding the core section and the outer shell section, the molding time can be shortened for even a thick item.