To produce an m-substituted styrene useful as an intermediate for a medicine or an agrochemical in high yield by a simple process consisting only of dehydrohalogenation of an m-substituted-α halostyrene.

This m-substituted styrene of formula II is obtained by carrying out dehalogenation on an m substituted-α-styrene of formula I (X is F, Cl, Br or trifluoromethyl; Y is Cl or Br, but the case where X is Br and Y is Cl is excluded) selectively at the α-position of the styrene of formula I. In the dehalogenation, a metal selected from the elements in the groups 1, 2, 8, 11 and 12 (especially, Mg, Fe, Cu, in, etc., is preferable) is used in an amount of 0.8-1.5 equivalent based on the compound of formula I. Further, the dehalogenation may be carried out by catalytic hydrogenation in the presence of a base. The catalytic hydrogenation is preferably performed using a catalyst such as a Raney nickel car Pd/C. Furthermore, the reaction can be applied in the case where a substituent at an m-position is a trifluoromethyl group.