In a fuel cell, a porous portion is formed in a separator. At a surface of the porous portion opposite to a surface where a reactant gas passage is formed, a cooling gas passage is formed. The cooling gas passage may be fluidly connected to a reactant gas supply passage for supplying reactant gas to the fuel cell. The cooling gas passage is controllable in flow amount. The porous portion is formed only in a separator portion where a downstream portion of the reactant gas passage is located. At a separator portion where an upstream portion of the reactant gas passage is located, a coolant passage is formed. A rib and a rib-bottom portion have a great porosity. A groove may be filled with porous material. The porous portion may be replaced by a water exchange portion. A portion of the separator other than the region of the porous portion may be made by porous material. Due to these, a fuel cell can be obtained where removal of product water is improved, product water can be utilized for humidifying gas, and product water can be uniformly removed.