The purpose of the present invention is, in powder hair dye compositions that contain a percarbonate, to suppress deterioration of coatability in long-term storage and also to ameliorate hair stiffening after hair dyeing treatment. To solve the aforementioned problem, a powder hair dye composition containing (A) a percarbonate and (B) a water-soluble polymer compound is provided, characterized by containing, as the water-soluble polymer compound (B), microorganism-derived/produced mucilage or chitosan containing (b1) glucose as a constitutive sugar, and (b2) a starch. With this powder hair dye composition, it is possible to suppress reduction in coatability in long-term storage under high-temperature, high-humidity conditions, and also to ameliorate hair stiffness after hair dyeing treatment.
