NOVELTY - Fuel cell has membrane-electrode assembly (MEA), and separator (18) with inlet (27b), outlet and passage (27a) for fuel gas, and inlet, outlet and passage for oxidant gas. MEA and separator are layered so that passage of fuel and oxidant gases are disposed in vertical plane. Inlet, outlet and passage of fuel and oxidant gases are arranged so that humidity distribution of gases are counter to each other.    USE - For vehicle.    ADVANTAGE - The humidity distribution at electrolyte membrane is uniform, and product water is smoothly exhausted from fuel cell. Since the fuel gas flow and oxidant gas flow are counter to each other, the wettest portion of one gas passage corresponds to the driest portion of other gas passage, and water circulation is effectively conducted. Since the coolant and oxidant gas flow are parallel with each other, the oxidant gas is effectively cooled by the coldest water near oxidant gas inlet. Therefore, the saturation vapor pressure is lowered near oxidant gas inlet, and drying-out of membrane near oxidant gas inlet is prevented. Since oxidant gas is cooled by the water, the saturation vapor pressure is raised near the oxidant gas outlet, and flooding near oxidant gas outlet is prevented.    DETAILED DESCRIPTION - The polymer electrolyte fuel cell comprises MEA including electrolyte membrane (11) whose one side is provided with anode (14) and another side with cathode (17). The separator includes inlet, outlet and passage for fuel gas and oxidant gas. MEA and separator are layered in a direction perpendicular to a gravity direction such that passage of fuel and oxidant gases are disposed in vertical plane. The inlet, outlet and passage of fuel and oxidant gases are arranged such that humidity distribution of fuel gas at anode and humidity distribution of oxidant gas at cathode are counter to each other. Each fuel and oxidant gas passage optionally has U-turn portion.    DESCRIPTION OF DRAWING(S) - The figure shows the cross-sectional view of one portion of fuel cell.    Electrolyte membrane (11)    Anode (14)    Cathode (17)    Separator (18)    Fuel gas passage (27a)    Fuel gas inlet (27b)