An object of the present invention is to provide a cosmetic composition containing a copolymer, a hair cosmetic and a hair treatment cosmetic, each of which is excellent in the adsorption amount of a cationic surfactant and also in the viscosity or smoothness upon application when used as a hair cosmetic. The present invention relates to a cosmetic composition comprising: a copolymer having a constituent unit corresponding to (A) a vinyl monomer having a carboxyl group in a structure and a constituent unit corresponding to (B) a vinyl monomer represented by the following formula (1)； a cationic surfactant； a higher alcohol； and a silicone oil: €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒCH 2 =C(R 1 )-CO-X-(Q-O) r -R 2 €ƒ€ƒ€ƒ€ƒ€ƒ(1) (wherein R 1 is a hydrogen atom or a methyl group； R 2 is a hydrogen atom or an alkyl group having a carbon number of 1 to 5, each of which may have a substituent； Q is an alkylene group having a carbon number of 2 to 4, which may have a substituent； r represents an integer of 2 to 15； and X represents an oxygen atom or NH, and the number of atoms bonded linearly to each other in the structure of -(Q-O) r -R 2 is 70 or less).
