To obtain a hair dressing resin composition hardly causing a flaking phenomenon and excellent in touch feeling, material felling and hair dressing properties by making the composition contain a copolymer obtained by using each specific monomer containing a betaine group, monomer containing a tertiary amino group, and other monomer in a specific ratio.

This hair dressing resin composition contains a copolymer obtained by using (A) 25-80wt.% monomer containing a betaine group of formula I [R1 is H or methyl; A is O or NH; (n) is 2, 3], (B) 5-60wt.% monomer containing a tertiary amino group of formula II (B is O or NH) and (C) 10-60wt.% other monomer of formula III (R2 is a 1-18C alkyl or a cycloalkyl). Further, the monomer of the formula I is obtained by reacting with heating N,N-dimethylaminoethyl(meth)acrylate with a haloacetic acid compound of the formula: X-CH2-COOM (X is a halogen; M is H or an alkali metal atom) in a nonaquenous solvent and then removing ionic impurities by a desalting treatment, and also it is preferable to copolymerize the components (A) to (C) in a hydrophilic solvent.