A process for producing 4,4'-dihydroxydiphenyl which comprises subjecting to alkali fusion 1 mol of 4,4'-diphenyldisulfonic acid and/or potassium 4,4'-diphenyldisulfonate together with 4 to 10 mol of potassium hydroxide and 0.1 to 2 mol of potassium sulfate. Alternatively, the process may comprise subjecting to alkali fusion 4,4'-diphenyldisulfonic acid in the presence of potassium hydroxide, controlling to 20 to 25% the potassium hydroxide concentration in the reaction mixture, and separating dipotassium salt of 4,4'-dihydroxydiphenyl.