NOVELTY - A metal ion of cerium, thallium, manganese, silver and ytterbium is supplied to stack cell of the fuel cell main component of polymer electrolyte fuel cell electric power generation system (100), and polymer electrolyte fuel cell electric power generation system is maintained. The polymer electrolyte fuel cell electric power generation system has stack laminated by cells (111) which interposed the solid polymer electrolyte by oxidation pole and fuel electrode, a separator (112), an oxidation gas supply unit and fuel gas supply unit (131).    USE - Method for maintaining polymer electrolyte fuel cell electric power generation system.    ADVANTAGE - The method provides polymer electrolyte fuel cell electric power generation system having excellent electric power generation property. The polymer electrolyte fuel cell electric power generation system suppresses deterioration of solid polymer electrolyte.    DETAILED DESCRIPTION - A metal ion of cerium, thallium, manganese, silver and ytterbium is supplied to stack cell of the fuel cell main component of polymer electrolyte fuel cell electric power generation system, and polymer electrolyte fuel cell electric power generation system is maintained. The polymer electrolyte fuel cell electric power generation system has stack laminated by cells which interposed the solid polymer electrolyte by oxidation pole and fuel electrode, a separator, an oxidation gas supply unit and fuel gas supply unit. The oxidation gas supply unit supplies fuel gas containing hydrogen to the oxidation pole of the stack cell. The fuel gas supply unit supplies fuel gas containing hydrogen to the fuel electrode of the stack cell of the fuel cell main component. An INDEPENDENT CLAIM is included for the polymer electrolyte fuel cell electric power generation system.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the polymer electrolyte fuel cell electric power generation system. (Drawing includes non-English language text)    Polymer electrolyte fuel cell electric power generation system (100)    Fuel cell main component (110)    Cell (111)    Separator (112)    Fuel gas supply portion (131)    Blower (132)