NOVELTY - The polymer electrolyte fuel cell has an electrolyte film (20), catalyst electrode layer (22,24), and gaseous-diffusion layers (I,II) (26,14). The area of lamination of surface of gaseous-diffusion layer (II) is smaller than catalyst electrode layer and layer (I). layer (II) is arranged such that the entire outer periphery overlaps on the surface of catalyst electrode layer and layer (I). The fuel cell is provided with a gas supply portion which supplies to layer (II) a gas for electrochemical reaction advancing in the catalyst electrode layer.    USE - For electric-power generation.    ADVANTAGE - The polymer electrolyte fuel cell ensures favorable gas utilization rate while gas is supplied to the catalyst electrode layer through the porous layer. Damage to the electrolyte film is suppressed. The electric-power-generation efficiency and durability of fuel cell are improved. Gaseous-diffusion layer (I) has excellent corrosion resistance in strongly acidic environment.    DETAILED DESCRIPTION - The polymer electrolyte fuel cell has an electrolyte film (20) consisting of solid polymer, a catalyst electrode layer (22) formed on both surfaces of the electrolyte film, gaseous-diffusion layer (I) (26) laminated on the outer side of the catalyst electrode layer, and gaseous-diffusion layer (II) (14). Gaseous-diffusion layer (I) is formed of an electroconductive porous component. The area of lamination of surface of gaseous-diffusion layer (II) is smaller than the catalyst electrode layer and gaseous-diffusion layer (I). Gaseous-diffusion layer (II) is arranged such that the entire outer periphery overlaps on the surface of catalyst electrode layer and gaseous-diffusion layer (I). The fuel cell is provided with a gas supply portion which supplies to gaseous-diffusion layer (II) a gas for electrochemical reaction advancing in the catalyst electrode layer.    DESCRIPTION OF DRAWING(S) - The figure shows the explanatory drawing of the fuel cell.    Membrane electrode assembly (12)    Gaseous-diffusion layers (14,26)    Seal portion (16)    Electrolyte film (20)    Catalyst electrode layer (22)