A hair treatment process comprises the following steps A or B, and includes conducting shaping of hair in at least one of the steps: Steps A: A first pack with a reducing agent contained therein and a second pack with an oxidizing agent contained therein, said second pack having buffer capacity and a pH of from 1 to 5, are successively applied to the hair, and the hair is rinsed with water and is dried (the first pack or the second pack contains an organic acid (A) or a salt thereof), Steps B: A first pack with a reducing agent contained therein, an intermediate treatment having buffer capacity and a pH of from 1 to 5, and a second pack with an oxidizing agent contained therein are successively applied to the hair, and the hair is rinsed with water and is dried (the first pack or the intermediate treatment contains the organic acid (A) or salt thereof), Organic acid (A): a compound comprising a non-aromatic hydrophobic group having a total carbon number of from 3 to 11 or an aromatic hydrophobic group having a total carbon number of from 4 to 18 and an acidic group such as a sulfo group, sulfate ester group or the like. By a procedure as simple as conventional straight perm, an extremely high, extremely curly hair correcting effect can be obtained. Further, subsequent to the treatment, the corrected state can be restored or maintained by a routine aftercare without damaging the hair.