The purpose of the present invention is to provide a cosmetic composition, a hair cosmetic and a hair treatment cosmetic, each of which is superior in the adsorption amount of a cationic surfactant and is also superior in the viscosity or smooth sensation upon application when used as a hair cosmetic, and which contains a copolymer. The present invention relates to a cosmetic composition which comprises a copolymer having a constituent unit corresponding to a vinyl monomer (A) having a carboxyl group in the structure thereof and a constituent unit corresponding to a vinyl monomer (B) represented by formula (1), a cationic surfactant, a higher alcohol and a silicone oil. CH2=C(R1)-CO-X-(Q-O)r-R2 (1) (In the formula, R1 represents a hydrogen atom or a methyl group； R2 represents a hydrogen atom or an alkyl group having 1-5 carbon atoms, both of which may have a substituent； Q represents an alkylene group having 2-4 carbon atoms which may have a substituent； r represents 2-15； and X represents an oxygen atom or NH； wherein the number of atoms that are bound linearly in the structure -(Q-O)r-R2 is 70 or less.)
