This invention provides a highly reliable separator integrated gasket for fuel cells free from deformation of a separator in a gasket molding process. In order to achieve the object, a pair of separators having adjacent portions approaching each other and separation portions separating from each other in a stacked state and having manifold holes opened in the separation portions are stacked via a spacer in which an inner peripheral hole is opened and which enables the circulation of a fluid in a direction orthogonal to the stacking direction so that the manifold hole and the inner peripheral hole are continuous to each other, a stacked object of the separators and the spacer is disposed in a mold, and then a rubber molding material is charged into and cured in gasket molding cavities defined between a surface opposite to the spacer in the separator and the mold.