To provide a method for inhibiting formation of a copolymer of divinylbenzene, formed by the manufacture of an aromatic vinyl compound or intermixed as an accompaniment of manufacturing raw materials of the aromatic vinyl compound, with an aromatic vinyl compound, and a method for inhibiting stains by deposition of the copolymer on apparatuses or equipments in a distillation process, a purification process or a storage process of the aromatic vinyl compound.

(A) a 2,6-dinitrophenol polymerization inhibitor and (B) at least one selected from among a nitroxy compound, a nitroso compound and hydroxylamine compound are simultaneously added in a manufacturing process, the purification process or the storage process of the aromatic vinyl compound. Preferably, (A) and (B) are used in a weight ratio of 99:1-70:30.