In a polymer electrolyte membrane type fuel cell employing a high polymer ion exchange membrane as an electrolyte, a fuel cells stack is produced at a low cost by easily constituting flow passages for a fuel gas, an oxidizing agent gas and a cooling water which have been conventionally constituted by a cutting process being hard to process and hard to reduce a cost. The fuel gas passage, the oxidizing agent gas flow passage and the cooling water flow passage are constructed by a combination of a diffuser constituted by a conductive porous body or a corrugated plate and an elastic gasket, whereby a cutting process is not required, and a number of parts can be reduced and an operating performance can be improved by integrally forming the gasket with the separator, so that a cost can be reduced.