PURPOSE: To enhance the molding efficiency of a molded product having a hollow part by arranging a foamed object molded from a solvent-soluble or hot-melt polymer in a mold as a core and supplying a reactive liquid raw material into the mold to mold a reaction injection molded product and taking out the molded product from the mold before removing the core by solvent treatment or heat treatment.

CONSTITUTION: A foam core 1 molded from a solvent-soluble or hot-melt polymer is arranged in a mold wherein an aluminum foil 5 is bonded to the inner surface of a wood mold formed from a wood retaining mold 3. A reactive solution 2 prepared by mixing a plurality of reactive raw materials is introduced into the mold and cured to obtain a molded product having a hollow part. The core of the molded product taken out of the mold is dissolved by a solvent or melted by a heating means 1 to be removed. Therefore, the molding efficiency of the molded product is improved.