PURPOSE: To obtaina natural composite body without fitting process and adhesion process by arranging containers with perforated holes in the mold cavity formed by a core mold and a cavity mold, supplying expandable resin beads between the core mold and the container through the perforated holes and pressure-molding it.

CONSTITUTION: A container provided previously with perforated holes is arranged on the side of the cavity mold in the mold cavity formed by a core mold and a cavity mold. Then, expandable resin beads are supplied fully between the core mold and the container through the perforated holes, heated, molded to form a composite foamed body having a foam inside the container. That is, a polypropylene molded piece 3 with perforated holes 4 are arranged in the mold cavity provided between the cavity mold 1 and the core mold 2. Then, feeders 5 are stuck tightly to the respective perforated holes 4, the space part provided between the core mold 2 and the polypropylene foam 3 is filled with expandable polystyrene beads through the perforated holes 4 and then the beads are heated by steam, molded to obtain an integral molding incorporated by the polypropylene molded piece 3 and a polystyrene foamed piece 6.