PROBLEM TO BE SOLVED: To provide a copolymer for detergent compositions excellent in finger combing and sliding properties when washing and rinsing, and feels such as softness after drying.SOLUTION: The invention provides a copolymer for detergent compositions consisting of the copolymer having a unit from the formula (1), (2), and other ethylenic unsaturated monomer. [Ris H or methyl Rto Rare an alkyl group and the like Xis Halogen anion or monoalkyl sulfate ester anion n is an integer of 1-10 Y is NH or O] [Ris H or methyl Mis H, an alkyl metallic cation, or onium cations]