METHOD FOR PRODUCING AROMATIC OLIGOMER

PROBLEM TO BE SOLVED: To enable reuse of acid catalysts used for a condensation reaction and reduce acidic waste water treatment used for the condensation reaction. SOLUTION: This method for producing a polycyclic aromatic oligomer comprises reacting a bicyclic or tricyclic aromatic compound or the aromatic compound and phenols with formaldehydes in the presence of an acid catalyst while removing water produced by the condensation reaction to the outside of the reaction system, separating an aqueous solution layer containing the acid catalyst from an organic layer and reusing the aqueous solution layer as the acid catalyst.