PURPOSE: To obtain an aromatic amine containing a substituted or nonsubstituted alkylthio group capable of stably and efficiently producing an aromatic polythiazole precursor without preparing an insoluble component as by-product.

CONSTITUTION: An aromatic amine shown by formula I or formula II (Ar is aromatic ring-containing residue; R is substituted or nonsubstituted alkyl) such as a compound shown by formula III. The compound shown by formula I is obtained by reacting an aromatic diaminodithiol or a salt thereof with an alkyl halide containing a substituted or nonsubstituted alkyl group in an alkali aqueous solvent preferably in the presence of a phase transfer catalyst to replace H atom of thiol group of the aromatic diaminodithiol or the salt thereof with an alkyl.