PURPOSE: To multilayer-mold a rubber molded product with uniform boundary surfaces without requiring adhesives by putting a separator into a mold, introducing non-vulcanizing rubbers each having different properties, removing the separator and molding said non-vulcanizing rubbers.

CONSTITUTION: A bottom force 2, an intermediate force 8 and a top force 10 are combined and a fluid path 6 is supplied with a pressure fluid and a separator 20 is positioned at the position of elevation, a non-vulcanizing rubber A is charged into an inserting section 12 for the top force 10 and a non-vulcanizing rubber B into an inserting section 13, and a support frame body 17 is lowered, thus pushing the non-vulcanizing rubbers A, B. Consequently, the non-vulcanizing rubber A is injected and filled into a partition chamber 21 of a cavity 16 and the non-vulcanizing rubber B into a partition chamber 22 of the cavity. The separator 20 is retreated to the outside of the cavity, and the non-vulcanizing rubbers A, B are injected to a formed space section. Each partial product section is co-vulcanized and unified.