PROBLEM TO BE SOLVED: To provide a hair straightening method and a hair treatment agent, in which the hair is difficult to handle in an intermediate washing step and a drying step, and the shortcomings of the hair straightening which are thermally damaged by the drying step and the ironing step are reduced. A hair straightening method includes a reducing step using a reducing agent, a hair strengthening step containing levulinic acid, an intermediate water washing step, a drying step, an ironing step, an oxidizing step using an oxidizing agent, and a water washing step. [Selection diagram] None【課題】中間水洗工程及び乾燥工程における毛髪の扱いにくさと、乾燥工程及びアイロン工程により熱ダメージするという縮毛矯正の欠点を軽減した、縮毛矯正方法及び毛髪処理剤を提供する。【解決手段】縮毛矯正方法が、還元剤による還元工程→レブリン酸を含む毛髪強化工程→中間水洗工程→乾燥工程→アイロン工程→酸化剤による酸化工程→水洗工程を含む。【選択図】なし
