PURPOSE: To obtain the subject compound useful as an intermediate for fluorine- containing compounds from the corresponding alkene in relatively good yield with a high efficiency by using hydrofluoric acid as a fluorine source in a water- insoluble organic solvent together with a halonium ion generator.

CONSTITUTION: An alkene expressed by formula I (R1 to R4 are H, substituted or unsubstituted straight-chain or branched chain alkyl, aryl or further R1 and R2, R1 and R3, R2 and R4 and R3 and R4 each integrally may form a ring) is allowed to react with hydrofluoric acid and a halonium ion generator in the presence of preferably a phase-transfer catalyst and/or a metallic fluoride used together in a water-insoluble organic solvent at -75 to +50°C, preferably 0°C to ambient temperature to carry out regioselective halofluorination. Thereby, the objective compound expressed by formula II (X is iodine or bromine atom) is selectively and efficiently obtained. Furthermore, the aforementioned method has advantages because even the halofluorination of a substrate having functional groups readily affected by acids proceeds without any problem.