NOVELTY - The cell stack comprises a left supply right ejection separator (11) and a right supply left ejection separator (11'). An oxidizing-agent gas supply port (14) of separator (11) is connected with an oxidizing-agent gas passageway positioned in a direction parallel to electrolyte surface of fuel cell and a discharge port (15) is connected with passageway positioned in its opposite direction. The separator (11') has supply and discharge ports (14',15') connected with an oxidizing-agent gas passageway positioned in reverse directions as that of the separator (11).    USE - For flat-type fuel cell stack.    ADVANTAGE - The temperature gradient of electrolyte surface inside each fuel cell is reduced.    DETAILED DESCRIPTION - The flat type fuel cell stack has separator (11) with oxidizing-agent gas supply port (14) arranged on left side and an oxidizing-agent gas discharge port (15) arranged on right side. The separator (11') has oxidizing-agent gas supply port (14') arranged on the right side and oxidizing-agent gas discharge port (15') arranged on left side. Two oxidizing-agent gas supply main paths (1,1') and two oxidizing-agent gas ejection main paths (2,2') are provided to supply and eject the oxidizing-agent gas to and from the separators. Two oxidizing-agent gas supply branched paths (4,4') are provided for connecting the oxidizing-agent gas supply ports of the separators with the oxidizing-agent gas supply main paths. Two oxidizing-agent gas ejection branched paths (5,5') are provided for connecting the oxidizing-agent gas discharge ports of the separators with the oxidizing-agent gas ejection main paths.    DESCRIPTION OF DRAWING(S) - The figure shows a perspective view of the flat-type fuel cell stack.    Oxidizing-agent gas supply main paths (1,1')    Oxidizing-agent gas ejection main paths (2,2')    Oxidizing-agent gas supply branched paths (4,4')    Oxidizing-agent gas ejection branched paths (5,5')    Separators (11,11')    Oxidizing-agent gas supply ports (14,14')    Discharge ports (15,15')