The present invention provides a polymer functional film obtained by polymerizing and curing a composition including (A) a styrene-based monomer represented by Formula (HSM); (B) a crosslinking agent represented by Formula (CL); and (C) a polymerization initiator represented by Formula (PI-1) or (PI-2), and a method for producing the same: in which R1 represents a halogen atom or —N+(R2)(R3)(R4)(X1−); n1 represents an integer from 1 to 10; here, R2 to R4 each independently represent a particular substituent; X1− represents an organic or inorganic anion;L1 represents an alkylene group or an alkenylene group; Ra, Rb, Rc and Rd each independently represent a particular substituent; n2 and n4 each independently represent an integer from 1 to 10; X2− and X3− each independently represent an organic or inorganic anion; andR5 to R10 each represent a hydrogen atom or a particular substituent.