Perfluorovinyl ether copolymer having sulfonamide groups

A perfluorovinyl ether monomer represented by the following formula (1): wherein: m is an integer of from 0 to 5; n is an integer of from 1 to 5; and each of R and R independently represents a hydrogen atom, an unsubstituted or substituted C1-C10 hydrocarbon group, or a substituted silyl group, with the proviso that, when each of R and R is independently the hydrocarbon group or the substituted silyl group, R and R are optionally bonded together, thereby forming a ring. Also disclosed are a method for producing the perfluorovinyl ether monomer; a fluorinated polymer obtained from the monomer and a method for producing the same; a polymer film obtained from the polymer; a modified or crosslinked polymer film obtained from the polymer film; and a solid polymer electrolyte membrane obtained from the modified or crosslinked polymer film.