PURPOSE: To obtain the subject resin for a photo-setting colored resin free from a circular defect, not precipitating very small spherular materials, by copolymerizing a 2-hydroxyethyl acrylate with an acrylic acid and a disubstituted aminoalkylacrylamide, etc., under a specific condition.

CONSTITUTION: In copolymerizing a mixed solution containing (A) a 2- hydroxyethyl acrylate of formula I (R1 is H or CH3), (B) an acrylic acid of formula II (R2 is H or CH3) and (C) a monomer of formula III (R3 is H or CH3; R4 and R5 are each CH3 or C2H5; X is O or NH; Y is CH2CH2 or CH2CH2 CH2) [e.g. dimethylaminopropyl (meth)acylamide] while dripping the mixed solution to water or an organic solvent, the concentration of the component B in the mixed solution of the monomers to be dripped is increased continuously or stepwise and/or the concentration of the component C in the mixed solution of the monomers to be dripped is reduced continuously or stepwise to give the objective water-soluble resin useful for a photo-setting colored resin composition.