NOVELTY - The polymer electrolyte fuel cell is formed by combining membrane electrode assembly with electrode containing catalyst layer and electrolyte film. The electrolyte films or portion(s) of electrode contains tungsten and/or molybdenum. The polymer electrolyte fuel cell is provided with deterioration inhibitor containing transition-metal compound(s) excluding tungsten and molybdenum. The ratio of transition metal with respect to tungsten and/or molybdenum is 0.01-0.6.    USE - Polymer electrolyte fuel cell used as vehicle-mounted motive power source, fixation type electric power generation device, cogeneration system, electrode material, and electrolyte film for electrochemical device such as water electrolysis apparatus, hydrohalic-acid electrolyzer, brine-electrolysis apparatus, oxygen and/or hydrogen concentrator, humidity sensor and gas sensor.    ADVANTAGE - The polymer electrode fuel cell has excellent durability and reduced electrolyte deterioration.    DETAILED DESCRIPTION - The polymer electrolyte fuel cell is formed by combining membrane electrode assembly with electrode containing catalyst layer and electrolyte film. The electrolyte films or portion(s) of electrode contains tungsten and/or molybdenum. The polymer electrolyte fuel cell is provided with deterioration inhibitor containing transition-metal compound(s) excluding tungsten and molybdenum. The ratio of transition metal with respect to tungsten and/or molybdenum is 0.01-0.6. The transition metal is chosen from iron, copper, manganese, cerium, ruthenium, zirconium, nickel, cobalt, zinc and palladium. The tungsten compound is chosen from tungsten oxide, tungsten carbide, tungsten nitride and tungsten boride. The molybdenum compound is chosen from molybdenum oxide, molybdenum carbide, molybdenum nitride and molybdenum boride. A complex compound is formed by mixing tungsten compound or molybdenum compound and transition-metal compound in a solvent. The tungsten oxide is chosen from hydrated tungsten oxide, tungstic acid and metal tungstate. The metal in metal tungstate is alkali metal or alkaline-earth metal.