A base-material/gasket unit mold which can reduce molding failure occurrence is provided. The mold includes a first half mold including a base material holding portion arranged on a first parting surface to hold a base material, and a second half mold having a second parting surface and used together with the first half mold to close and open the mold. The second half mold includes a gasket cavity defined on the second parting surface side to form a gasket main body on a surface of the base material, an isolated rubber cavity forming an isolated rubber portion isolated from the gasket main body on the surface of the base material, and a mold-pressing portion arranged around the isolated rubber cavity to press the base material when the mold is closed and having a recessed part defined on a press surface side to reduce deformation of the base material.