To solve problem giving strong unpleasant odor to users when ammonia is frequently used as an alkali agent for hair treatment agent composition.This hair treatment agent composition comprises (A) an alkaline agent, (B) a base material and (C) a reducing agent. In the composition, each of the agents and material contains a specific component such as ammonia, an amine, hydrogen sulfide or mercaptan in an mount below the sensitivity of an olfactory organ of a human being. The inventive treatment agent composition generates no unpleasant odor when used and can comfortably be used and further can be produced with ease.
