Mold device, injection molding system and method for manufacturing molded article

A mold device having a nested structure used for a molding method where a pressurized fluid is injected into a clearance between a resin injected into a cavity and a cavity wall surface, the mold device comprising:

• a shaft body that is provided on at least one of a first mold and a second mold, the first mold and the second mold forming a molding space, the shaft body ejecting a molded article that is molded from the resin injected into the molding space;
• a ring-shaped elastic member for supporting and sealing the shaft body, an opening of a groove formed in the ring-shaped elastic member along a circumferential direction of the ring-shaped elastic member being oriented toward the molding space, a load being applied on the ring-shaped elastic member to improve adhesion to the shaft body;
• and
• an injection portion that is provided on at least one of the first mold and the second mold for injecting the pressurized fluid into the molding space, wherein
• the cavity wall surface subjected to fluid pressurization is embossed so that the pressurized fluid is injected into the clearance between the resin and an embossed portion of the cavity wall surface.