PURPOSE: To readily isolate and obtain the title compound useful as a dye, etc., by reducing naphthazarin with stannous chloride to provide a leuco compound and oxidizing the resultant leuco compound with air, etc., while refluxing the reaction mixture.

CONSTITUTION: Naphthazarin expressed by formula 2 is reduced with stannous chloride to provide a leuco compound expressed by formula 3. Aniline is then added thereto in the presence of a boron compound (e.g., boric acid, boron acetate or boron fluoride) and refluxing is carried out to oxidize the leuco compound with air and afford the aimed 4,8-bis(phenylamino)-1,5-naphthoquinone expressed by formula 1. The use of a solvent other than aniline is not required in refluxing for the reaction; however, ethanol is preferred in using the solvent.