PURPOSE: To provide a method for treating hair, capable of easily, simply and effectively improving the quality of hair and reducing the damage to the hair even outside a bath.

CONSTITUTION: When hair is treated with steam after or during a time when the hair is coated with a hair-treating agent, (A) a treating agent containing a compound of formula I (R1 is H, methyl; R2 is a 1-5C alkyl; (n) is 2-6), e.g. diethyleneglycol monoethyl ether, (B) a treating agent containing a compound of formula II (R3 is H, a 1-4C alkyl; R4 is COOH, SO3H), e.g. glycolic acid or lactic acid, and (C) a treating agent containing one or more of a naphthalene sulfonic acid compound, a benzophenone sulfonic acid compound, or an azulene sulfonic acid compound is used as the hair-treating agent. When the treating agent A is used, the generation of the split hair can especially be prevented. When the treating agent B is used, durable flexibility can be imparted to the hair. When the treating agent C is used, durable tension and stiffness can be given to the hair.