PROBLEM TO BE SOLVED: To develop a polymer for hair gloss comprising a novel copolymer and to provide hair cosmetics containing the polymer.SOLUTION: The copolymer is obtained by polymerizing a monomer composition including 5-90 mol% of a monomer M1 represented by specific formula (1), 5-90 mol% of an acrylic monomer M2 having a carbocyclic ring as a substituent, and 3-80 mol% of a monomer M3 having an amino group or an ammonium salt group as a substituent, wherein M1+M2+M3 is 50 mol% or more.COPYRIGHT: (C)2011,JPO&INPIT【課題】新規な共重合体からなる毛髪つや出し用ポリマーを開発し、これを含有する毛髪用化粧料を提供。【解決手段】特定の式(1)で表される単量体M1を5~90モル%と、炭素環を置換基として持つアクリル系単量体M2を5~90モル%と、アミノ基、アンモニウム塩基を置換基として持つ単量体M3を3~80モル%含み、M1+M2+M3が50モル%以上である単量体組成物を重合して得られる共重合体。【選択図】なし