. . . "A process for production of a styrene copolymer, comprising copolymerization of a styrene monomer represented by formula (I'): ##STR17## wherein R1 is a hydrogen atom, a halogen atom or a hydrocarbon group having not more than 20 carbon atoms, m is an integer of 1 to 3, and when m is plural, R1 s may be the same or different, and an unsaturated arboxylic acid or its ester monomer represented by fo" . . .