To obtain the subject compound useful as an intermediate for medicines and agrochemicals.

An α-bromoethylbenzene of formula I (R1 and R2 are each H or an electron attracting group not containing H in the group) is treated with bromine in the presence of a free radical initiator to give an α, β- dibromoethylbenzene of formula II. The compound of formula I is obtained by treating an ethylbenzene of formula III with bromine in the presence of a free radical initiator. The compound of formula III is dehydrobrominated to give an α-bromostyene of formula IV. An organic peroxide such as t- butylhydroperoxide or an azo compound such as azobisisobutyronitrile is preferable as the free radical initiator.