PURPOSE: To obtain high purity p-dichlorobenzene having a high p-content and a low m-content only by direct distillation by subjecting (chloro)benzene to ring chlorinating in a liq. phase in the presence of a Friedel-Crafts catalyst and a specified co-catalyst.

CONSTITUTION: (Chloro)benzene is subjected to ring chlorination in a liq. phase in the presence of a Friedel-crafts catalyst and a co-catalyst of the formula (where X is F, Cl, Br, trifluoromethyl or pentafluoroethyl and A is two H atoms or -CH=CH-CH=CH-) to obtain the objective p-dichlorobenzene. The reaction temp. is preferably 40-70°C. The amt. of the Friedel-Crafts catalyst used is 0.001-1 wt.%, preferably 0.01-0.1 wt.% of the amt. of the benzene, chlorobenzene or a mixture of them.