A hair deforming treatment agent comprising the following components (A), (B) and (C):(A) glyoxylic acid, or a hydrate or a salt thereof,(B) a compound represented by the following formula (1):wherein R1 represents H or a methyl group, A1, A2 and B each represent H, an alkyl group, an alkenyl group, etc., D represents H, OH, a methyl group, an alkoxy group, etc., and E represents H, a methyl group, an alkoxy group, etc., and(C) water.
