PURPOSE: To mold a final product of various kinds shapes out of an intermediate product of single shape by casting molten thermoplastic synthetic resin containing a foaming agent into a cavity of a first mold, cooling and molding a semi-cured intermediate molded product, transferring the same into a cavity of a second mold, foaming and molding into a final molding.

CONSTITUTION: Foamed resin is injected into a cavity 2 of a first cavity 1 by an injection molding machine, and a master 3 in the semi-cured state is released. Correction molds 4 and 5 as second molds consist top forces 4a and 5a and bottom forces 4b and 5b, and recessed sections 6 conforming with the final shape respectively are formed on mating surfaces of top and bottom forces 4a, 5a, 4b and 5b, which constitute second cavities 7 and 8. The cavities 7 and 8 are larger than the volume of a master, and desired recesses and projections 9 and pattern 10 are formed on its surface. When the master 3 is transferred to the correction molds 4 and 5, foaming is continued in the molten inner side and expanded, and the surfaces of correction molds are pressed to the surfaces of cavities 7 and 8 to manufacture a desired final product. The expansion ratio of the master 3 is 1.0 - 2.0, and the expansion ratio of the final molded product is 2.0 - 20.