NOVELTY - A fuel cell comprises valves (33, 34, 37, 38) for closing an anode electrode layer-side space defined by membrane electrode assembly (10), gas passageway of fuel-side separator (20) and hydrogen gas supply-discharge pipes (31, 35) and a cathode electrode layer-side space defined by membrane electrode assembly, gas passageway of oxidizer-side separator and air supply-discharge pipes (32, 36). The valves are in respective gas supply-discharge pipes. The closed anode electrode layer-side space has greater volume than the closed cathode electrode layer-side space.    USE - As a polymer electrolyte fuel cell or proton exchange membrane-type fuel cell.    ADVANTAGE - In a state where the fuel cell suspends generation of electricity, the closing component can close the anode electrode layer-side space, which is filled with fuel gas, and the cathode electrode layer-side space, which is filled with oxidizer gas. This can prevent introduction of new oxidizer gas into the cathode electrode layer-side space to limit the quantity of nitrogen gas in oxidizer gas present in the cathode electrode layer-side space. Even when cross-leak occurs between the cathode electrode layer-side space and the anode electrode layer-side space, the quantity of nitrogen gas that can permeate from the cathode electrode layer-side space to the anode electrode layer-side space can be limited, effectively suppressing an increase in the concentration of nitrogen gas in the anode electrode layer-side space. Immediately after start of operation of the fuel cell, fuel gas can be supplied to the anode electrode layer. The fuel cell can exhibit good starting characteristics and provide improved convenience.    DETAILED DESCRIPTION - A fuel cell comprises a membrane electrode assembly comprising an electrolyte membrane (11) formed of an ion exchange membrane, an anode electrode layer formed on one surface of the electrolyte membrane, and a cathode electrode layer formed on the opposite surface of the electrolyte membrane. Fuel-side and oxidizer-side separators provide gas passageways for introducing fuel gas and oxidizer gas into the membrane electrode assembly. Gas supply-discharge pipes externally supply the fuel gas and oxidizer gas to and discharge unreacted fuel gas and unreacted oxidizer gas from a fuel cell stack comprising cells each including the membrane electrode assembly and the separators. Valves close an anode electrode layer-side space and a cathode electrode layer-side space. The anode electrode layer-side space is defined by the membrane electrode assembly, the gas passageway of the fuel-side separator and the gas supply-discharge pipes. The cathode electrode layer-side space is defined by the membrane electrode assembly, gas passageway of the oxidizer-side separator and the gas supply-discharge pipes.    DESCRIPTION OF DRAWING(S) - The figure shows a sectional view of a single cell of a fuel cell.    Membrane electrode assembly (10)    Electrolyte membrane (11)    Catalyst layers (12, 14)    Gas diffusion layers (13, 15)    Separator (20)    Streaky recess portions (21)    Streaky projection portions (22)    Gas supply-discharge passageways (30)    Hydrogen gas supply-discharge pipes (31, 35)    Air supply-discharge pipes (32, 36)    Valves (33, 34, 37, 38)