PURPOSE: To raise the working efficiency by making the boundary of the primary and secondary rubber bases clear and adhering both rubber bases firmly.

CONSTITUTION: The lower mold b consists of the primary concave 1 for the primary rubber base (c) to be pressed into and the secondary concave 2 for the secondary rubber fabric d to be pressed into. On the other hand, the upper mold consists of the primary upper mold a-1 and the secondary upper mold a-2. The inner face 3 of primary upper mold forms the rubbing face against the upper edge 4 of primary concave, and forms the space against the upper edge of secondary concave. The inner face 6 of secondary upper mold forms the space against both of primary and secondary concaves. Meanwhile, the releasability of the surface 12 of lower mold concave 1 are formed inferior to that of the inner face of primary upper mold. Further, the releasability of each of inner faces of primary upper mold and secondary upper mold are formed inferior to that of other surfaces except the primary concave of lower mold. By the said formation, the unvulcanized rubber molding product is removed out of the mold easily and also deflashing is carried out easily, and the primary rubber base of different color and of different quality can be filled by one-time pressing.