To safely and inexpensively obtain the subject compound useful as a monomer for polybenzbisoxazole excellent as fiber by reducing meta- dinitrobenzene in a reaction medium and subjecting the reduced material to rearrangement reaction by heat, etc., without isolating a reaction intermediate.

(A) meta-Dinitrobenzene of formula I is reduced at 0-20°C by a metal powder reducing agent such as zinc in a heterogeneous two layer-based reaction medium of (i) an aqueous solution of inorganic electrolyte such as ammonium chloride and (ii) an organic solvent such as ether which dissolves the component A and is nonmiscible with water to afford meta- phenylenedihydroxylamine which is a reaction intermediate of formula II, and further the reaction intermediate is subjected to rearrangement reaction for 30-90 min while heating it under stirring by heat or (D) an acid catalyst such as sulfuric acid to provide the objective 4,6-diaminoresorcin of formula III. A molar ratio of the component C to the component A is preferably 0.8-4.0.