OPERATION METHOD OF POLYMER ELECTROLYTE FUEL CELL SYSTEM AND POLYMER ELECTROLYTE FUEL CELL SYSTEM

An operation method of a polymer electrolyte fuel cell system including an anode () supplied with a fuel gas containing hydrogen, a cathode () supplied with an oxidizing gas containing oxygen, and a polymer electrolyte membrane () sandwiched between the anode () and the cathode (), comprises supplying to the anode () the fuel gas humidified with a higher level than the oxidizing gas to cause the anode () to have a humidified state with a higher level than the cathode (), in start-up of the polymer electrolyte fuel cell system.