NOVELTY - A fuel cell (100) comprises electrolyte membrane, first reactive gas channel provided on first surface side of electrolyte membrane, second reactive gas channel provided on second surface side of the electrolyte membrane, in which second reactive gas flows. The flow direction of first reactive gas flowing in first reactive gas channel is opposite to flow direction of second reactive gas flowing in second reactive gas channel, where downstream portion of flow of first and second reactive gases, in a plane of the electrolyte membrane, is cooled more than a central portion within the plane.    USE - Fuel cell.    ADVANTAGE - The electrolyte membrane of the fuel cell is wetted, thus enhancing membrane and stabilizing power generation capacity.    DETAILED DESCRIPTION - The fuel cell (100) comprises electrolyte membrane, first reactive gas channel provided on first surface side of electrolyte membrane in which first reactive gas flows, second reactive gas channel provided on second surface side of the electrolyte membrane, in which second reactive gas flows, and coolant channel in which coolant flows. The flow direction of first reactive gas flowing in first reactive gas channel is opposite to flow direction of second reactive gas flowing in second reactive gas channel, where downstream portion of flow of at least one of the first and second reactive gases, in a plane of the electrolyte membrane, is cooled more than a central portion within the plane. An INDEPENDENT CLAIM is included for a fuel cell system (10) comprising the fuel cell, reactive gas supply portion (700) that supplies first and second reactive gases; and coolant supply portion (800) that supplies coolant. The electrolyte membrane is wetted by causing moisture contained in reactive gases to condensate by cooling downstream portion of at least one of the first and second reactive gas flows with coolant channel, without providing humidifying module for humidifying first and second reactive gases.    DESCRIPTION OF DRAWING(S) - The drawing is an explanatory schematic diagram illustrating the flow of coolant in the cell units that are stacked to form fuel cell.    Fuel cell system (10)    Fuel cell (100)    Fuel gas discharge manifold (120)    Gas supply portion (700)    Coolant supply portion (800)