To provide a mold apparatus capable of reducing effectively formation of an article defective in molding due to poor filling up of rubber upon molding a rubber molded article.

An inner pressure auxiliary material 4 which operates under facing to a cavity in an inner part of a mold is equipped in a mold. Unvulcanized rubber is filled up in the cavity, and then the auxiliary material 4 is allowed to operate in a projecting direction to give an inner pressure to the rubber in the cavity, whereby poor filling up of rubber can be cured.