MOLDING DIE AND SEAL PART

A molding die for molding, on a surface of a plate-like base material, an endless-shaped gasket made of an elastic material includes a cavity which is formed on the opposing surface opposed to the surface of the base material and corresponds to the shape of the gasket, a gate for introducing a molding material which is cured to become an elastic material, a first intermediate portion connecting a gate opening and the cavity and a cross section along the base surface has an area equal to or larger than an opening area of the gate opening, a vent discharging gas unnecessary for molding, and a second intermediate portion connecting an opening on the cavity portion side of the vent extending along the base surface and the cavity and a cross section along the base surface has a cross-sectional area equal to or larger than an area of the gate opening.