A fuel cell wherein efficient cooling is achieved by supplying air and cooling water simultaneously while maintaining cooling and wetting of a membrane without increasing the size of the fuel cell. The fuel cell includes a separator sandwiched between unit cells. The separator includes an air passage on a front surface side abutting at least on a cathode of the unit cell and cooling passages supplied with air and water on the rear side thereof to cool the unit cell with latent heat of evaporation of water by heat of the unit cell transmitted to the cooling space. Thereby, the unit cell is cooled via the separator and clogging of the air passages by water is prevented.