Problem: To provide a novel copolymer capable of use as a surface treatment agent which is safe and does not generate hydrogen, which has good compatibility with other cosmetic raw materials so as to be able to improve compounding stability of a cosmetic, which contributes to good water resistance, sebum resistance, gloss, feel, hair attachment ability, skin attachment ability and the like of a cosmetic, which further may be used for treatment of powders of a wide range of cosmetics, and which nearly entirely suppresses the occurrence of dispersion failure on the skin.Resolution Means: A copolymer comprising: (A) an unsaturated monomer having a carbosiloxane dendrimer structure； and(B) an unsaturated monomer having at least one hydrophilic group in the molecule.A content of the unsaturated monomer having the carbosiloxane dendrimer structure is in the range of 35 to 50% by mass of the total monomer units of the copolymer. The present invention is also a liquid composition, surface treatment agent, and powder composition including such a copolymer, as well as a cosmetic raw material containing such components.
