NOVELTY - The electrolyte film (1) has cathode side solid-polymer-electrolyte layer (10c), anode side solid-polymer-electrolyte layer (10a) and reinforcement layer (11). The reinforcement layer contains porous reinforcing material. The voids in reinforcement layer are filled with solid polymer electrolyte (10s). The cathode having water content larger than the volume of solid-polymer-electrolyte layer exists in the electrode side. The anode having water content larger than the volume of solid-polymer-electrolyte layer exists in the little electrode side.    USE - For polymer electrolyte fuel cell (claimed) and film and electrode assembly.    ADVANTAGE - The electrolyte film prevents the durable fall by dimensional change of film in film and electrode assembly. The manufacture of electrolyte film is simple. The polymer electrolyte fuel cell formed using the electrolyte film has excellent electrical power generation performance and durability. The fall of mechanical strength by film thinning is suppressed.    DETAILED DESCRIPTION - The electrolyte film has cathode side solid-polymer-electrolyte layer, anode side solid-polymer-electrolyte layer and reinforcement layer. The reinforcement layer contains porous reinforcing material. The voids in reinforcement layer are filled with solid polymer electrolyte. The cathode side solid-polymer-electrolyte layer is provided in the cathode side of reinforcement layer. The anode side solid-polymer-electrolyte layer is provided in the anode side of reinforcement layer. The cathode having water content larger than the volume of solid-polymer-electrolyte layer exists in the electrode side. The anode having water content larger than the volume of solid-polymer-electrolyte layer exists in the little electrode side.    DESCRIPTION OF DRAWING(S) - The figure shows the expanded sectional view of electrolyte film.    Electrolyte film (1)    Anode side electrolyte layer (10a)    Cathode side electrolyte layer (10c)    Electrolyte of reinforcement layer (10s)    Reinforcement layer (11)