To obtain a new fluorine-containing olefin which is useful as a monomer for polymers and as an intermediate for a variety of fluorine-containing compounds, for example, hydrofluorocarbons, medicines and agrochemicals.

This fluorine-containing olefin is represented by formula I [X is chlorine, fluorine; Y is chlorine, bromine, iodine; R1 and R2 are each H, a 1-10C alkyl or R1 and R2 link to each other to form the group of the formula: -(CH2)n- (n is 3-7)], typically 3-trifluoromethyl-1,1,1-trifluoro-2,4-dichloro-2-butene. The compound of formula I is obtained by reaction of a compound of formula II (Rf and Rf' are each trifluoromethyl; Z is hydroxyl, sulfonate group) with a halogenating agent (for example, in the case that Z is OH, the agent is a hydrogen halide, phosphorus halide, while in the case that Z is a sulfonate, it is an alkali halide).