NOVELTY - A solid polymer electrolyte film (11) contains a composition of phosphoric acid group-containing polymer (A), a phosphoric acid/sulfonic acid group-containing copolymer (B) and/or a sulfonic acid group-containing polymer (C), and a polyamide resin (D). Copolymer (B) is obtained by copolymerizing a phosphoric acid group-containing unsaturated monomer (UM) and UM having sulfonic acid group(s) and ethylenically unsaturated bond(s).    USE - Used for a fuel cell (claimed), especially a direct methanol fuel cell, primary and secondary batteries, display device, signal transmission medium, solid capacitor, ion exchange membrane and sensor.    ADVANTAGE - The solid polymer electrolyte has good heat resistance, chemical resistance, mechanical strength, water resistance, flame retardance, transparency and high proton conductivity over a large temperature and humidity range. The polymer electrolyte is manufactured safely.    DETAILED DESCRIPTION - A solid polymer electrolyte film (11) contains a uniform composition of a phosphoric acid group-containing polymer (A), a phosphoric acid/sulfonic acid group-containing copolymer (B) and/or a sulfonic acid group-containing polymer (C), and polyamide resin (D). The polymer (A) is obtained by polymerizing an unsaturated monomer having phosphoric acid group(s) and ethylenically unsaturated bond(s). The copolymer (B) is obtained by copolymerizing a phosphoric acid group-containing unsaturated monomer and an unsaturated monomer having sulfonic acid group(s) and ethylenically unsaturated bond(s). The polymer (C) is obtained by polymerizing a sulfonic acid group-containing unsaturated monomer.    INDEPENDENT CLAIMS are also included for the following:    (1) a solid polymer electrolyte composite film; and    (2) a fuel cell (1).    DESCRIPTION OF DRAWING(S) - The figure shows a sectional view of the fuel cell using the solid polymer electrolyte film.    fuel cell (1)    separator (2)    solid polymer electrolyte film (11)    catalyst electrodes (12a,12b)