An oxidant gas conduit communicating with both an oxidant gas inlet communication hole and an oxidant gas outlet communication hole is formed in a surface of a cathode-side metallic separator which forms a fuel cell. Continuous linear guide ridges which protrude from intermediate height sections to the oxidant gas conduit side and form continuous guide conduits are provided on the cathode-side metallic separator. The linear guide ridges are continuously connected to ends of rectilinear conduit ridges which form rectilinear conduits, are provided with bend portions, and are set to lengths which are different from each other in a step-like manner.