PURPOSE: To enable mass production of articles with uniform dimensions along with labor-saving, by a method wherein a process performing reaction molding by casting a liquid material by performing mold clamping of a core mold and each of cavities is executed by exchanging each of the cavities in order an N-layer laminated molded article is formed and at least up to a product of an N-1 layers the same is kept stuck to the core mold as it is.

CONSTITUTION: An insertion liquid material is cast after a core mold 2 and insertion cavity mold 3 have been clamped by mating them together and an insert G1 is molded within a cavity formed by the core mold 2 and cavity mold 3. Then both the cavity molds 3, 6 are shifted leftward, the cavity mold 6 for soft urethane is set up at a fixed position of the lower part of the core mold 2 by removing the insertion cavity mold 3, the core mold 2 is clamped to the cavity mold 6 by actuating an RIM molding press 1 and a soft urethane material is cast into a cavity between the insert G1 and cavity mold 6 through a mixing head 5. The insertion cavity mold 3 is stopped at a fixed position of the lower part of the core mold 2 and an insert-filled molded article G is unloaded through the removed cavity mold 6. Therefore, manufacture of an insert-filled RIM molded article becomes possible by one device.