A hair dye composition comprising the following component (A) and the alkaline agent (B), as defined below, and a further alkaline agent other than component (B), in which the mass ratio of the component (B) to the component (A), (B)/(A), in a whole composition is 1 or more and 100 or less, the mass ratio of the component (B) relative to an alkaline agent other than the component (B) [component (B)]/[alkaline agent other than component (B)] is from 0.5 to 3.5, and the pH (25°C) during application is 7.5 to 12:(A): one or more azo dyes selected from the group consisting of the following (A-1), (A-2) and (A-3):(B): at least one member selected from the group consisting of guanidine carbonate, guanidine hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate and lithium carbonate.
