PROBLEM TO BE SOLVED: To provide an oxidation hair dye composition which contains a carbonate as an alkali agent, can thereby impart good brightness to hair, and can ensure a sufficient hair-dyeing force.SOLUTION: The oxidation hair dye agent composition comprising (A) an alkali agent containing at least a carbonate, (B) an oily ingredient, (C) a surfactant, (D) a chelate agent, and (E) an oxidizing agent is characterized by having a component content mass ratio (B)/(C) of 2-4.5 and having a (D) component content of 0.2-0.5 mass%.