A two-part hair dye composed of a first part containing an alkali agent, a second part containing hydrogen peroxide, and a non-aerosol foamer container for discharging a liquid mixture of the first part and the second part in the form of a foam, the liquid mixture containing the following components (A) and (B): (A) a polymer or copolymer containing 70% or more mole fraction of diallyldimethyl quaternary ammonium salt monomer, and (B) an N-acylamino acid salt, an N-acyl-N-alkylamino acid salt, or an ether carboxylic acid salt, wherein, an equivalent ratio of the anion site of the component (B) to the cation site of the component (A) (anion/cation) is more than 1, and a viscosity of the liquid mixture at 25° C. is 1 to 300 mPa·s.