To enhance P-position selectivity in nucleus chlorination and enable recovery of catalyst and reuse of the catalyst by using a Lewis acid catalyst supported on a polymer when the nucleus of benzene or its derivative is chlorinated with chlorine gas.

The nucleus of benzene or its derivative is chlorinated with chlorine gas using a Lewis acid supported on a polymer. Granular styrene- divinylbenzene copolymers obtained by copolymerizing 5-20wt.% divinylbenzene or its derivative, having ≤150μm particle diameter and having pores with ≤30nm average pore diameter measured by a constant flow rate method by a precise gas adsorption device are preferably used as the Lewis acid catalyst supported on the polymer. Aluminum chloride is preferably used as the Lewis acid. Lewis acid is supported in an amount of 5-10 pts.wt. based on 100 pts.wt. polymer. The Lewis acid catalyst supported on the polymer is preferably used in an amount of 50-300mg based on 1mol benzene or its derivative, expressed in terms of Lewis acid amount.