The present invention is a cosmetic composition for hair for cleansing and conditioning hair fibers, particularly human hair fibers, comprising an anionic surfactant, an amphoteric surfactant, thiolactic acid, a thiolactic acid derivative, salts thereof, And a thiol-based compound selected from these, a thickener; a nonionic surfactant; and water; and a cosmetic composition for hair, wherein the pH of the composition is in the range of less than about 2-7 . The present invention also provides a method for imparting hair care benefits such as straightening effects, volume reduction, curly hair control, ease of handling, cosmetics and smooth feel, as well as cleansing and conditioning benefits to the hair fiber, and It relates to the use for hair care with the cosmetic composition of the invention.本発明は、毛髪繊維、特にヒト毛髪繊維をクレンジング及びコンディショニングするための毛髪用化粧用組成物であって、アニオン性界面活性剤、両性界面活性剤、チオ乳酸、チオ乳酸誘導体、これらの塩、及びこれらの混合物から選択されるチオール系化合物、増粘剤;非イオン性界面活性剤;並びに水を含み;組成物のpHが約2~7未満の範囲である、毛髪用化粧用組成物に関する。本発明はまた、ストレート化効果、ボリューム減少、縮毛制御、扱いやすさ、化粧性、及び滑らかな感触等の毛髪ケアの利益、更にクレンジング及びコンディショニングの利益を毛髪繊維へ付与する方法、並びに本発明の化粧用組成物を用いた毛髪ケアのための使用に関する。