Separators for unit cells of a fuel cell each have a plurality of through holes extending therethrough and a recessed portion formed in a surface thereof. In a fuel cell incorporating such separators, the recessed portion of each separator forms an in-cell oxidative gas passage, together with an adjacent cathode. An oxidative gas, supplied from an external device into the fuel cell, is distributed from an oxidative gas supply manifold formed by holes of the separators, to the in-cell oxidative gas passages. The oxidative gas is then collected in an oxidative gas discharge manifold formed by holes of the separators, and conveyed out of the fuel cell by the discharge manifold. During the passage through each in-cell oxidative gas passage, the oxidative gas flows via an oxidative gas transit manifold formed by holes of the separators.