In a process for producing an anthraquinone dye intermediate, 1,4-diamino-2,3-dicyanoanthraquinone, by reacting 1,4-diaminoanthraquinone-2-sulfonic acid, a salt thereof, 1,4-diaminoanthraquinone-2-cyanoanthraquinone, 1,4-diamino-2,3-disulfonic acid, or a salt thereof with a cyanogenating agent in an aqueous medium, the yield and quality of the product can be improved markedly by carrying out the reaction in the presence of a quaternary ammonium compound, and further, depending upon the starting material used, in the presence or absence of a dehydrogenating agent.