A hair deformation treatment agent that contains components (A), (B), and (C), wherein the mole ratio (B)/(A) of component (B) content to component (A) content is 0.2-5. (A) Glyoxylic acid or a hydrate or salt thereof. (B) Resorcin. (C) Water.本發明之毛髮變形處理劑含有以下之成分(A)、(B)及(C),且成分(B)之含量相對於成分(A)之含量的莫耳比(B)/(A)為0.2以上且5以下。(A)乙醛酸或其水合物或鹽(B)間苯二酚(C)水