To provide a method for producing a diarylsulfone polycarboxylic acid or its anhydride which is a valuable material having a wide application field.

The method for the production of the diarylsulfone polycarboxylic acid expressed by general formula (3) (Ar is benzene ring or naphthalene ring; and (n) is an integer of 1-3) or its anhydride comprises a sulfide dimerization process to obtain a diarylthiopolycarboxylic acid or its anhydride by the reaction of an aromatic carboxylic acid of general formula (1) (Ar and (n) are same as those defined above; X is nitro or a halogen), its anhydride or its 1-8C alkyl ester with sulfur or a sulfide and an oxidation process to oxidize the obtained diarylthiopolycarboxylic acid or its anhydride with an oxidizing agent.