NOVELTY - A solid polymer electrolyte film is obtained by polymerizing a phosphoric acid group-containing unsaturated monomer (A) and an amino group-containing unsaturated monomer (B). Monomer (A) has phosphoric acid group and ethylenically unsaturated bond(s) in a molecule. Monomer (B) has (un)substituted amino group and ethylenically unsaturated bond(s) in a molecule.    USE - For fuel cell (claimed) such as direct methanol fuel cell, and for primary battery, secondary battery, display element, sensor, signal transmission medium, solid capacitor and ion exchange membrane.    ADVANTAGE - The solid polymer electrolyte film having improved solvent resistance and proton conductivity in wide temperature region, is manufactured economically. Temperature dependency of proton conductivity is reduced.    DETAILED DESCRIPTION - A solid polymer electrolyte film is obtained by polymerizing a phosphoric acid group-containing unsaturated monomer (A) and an amino group-containing unsaturated monomer (B). Monomer (A) has phosphoric acid group and ethylenically unsaturated bond(s) in a molecule. Monomer (B) has (un)substituted amino group and ethylenically unsaturated bond(s) in a molecule. Portion(s) of hydroxyl group in the phosphoric acid group is reacted with amino group, and has quaternary ammonium salt group. INDEPENDENT CLAIMS are included for the following:    (1) monomer composition for solid polymer electrolyte, which is obtained by modifying phosphoric acid group-containing unsaturated monomer and amino group-containing unsaturated monomer;    (2) manufacture of solid polymer electrolyte film, which involves polymerizing the monomer composition, or copolymerizing the monomer composition and another copolymerizable unsaturated monomer; and    (3) fuel cell, which has the solid polymer electrolyte film.    DESCRIPTION OF DRAWING(S) - The figure shows the side view explaining the state, which interposed the solid polymer electrolyte composition between glass flat plates.    solid polymer electrolyte composition (1)    glass flat plate (2)    clip (3)