A method for preparing optically active 1-bromo-1-[3,5-bis(trifluoromethyl)-phenyl]ethane having a high optical purity, which comprises the step of brominating optically active 1-[3,5-bis(trifluoromethyl)phenyl]ethanol by using, as a brominating agent, (a) a combination of a phosphorus halide and hydrogen bromide, (b) a combination of 1,2-dibromo-1,1,2,2-tetrachloroethane and an organic phosphorous compound represented by the general formula (I): P(R1)(R2)(R3) (in the formula, R1, R2, and R3 independently represent a C6-10 aryl group, a C6-10 aryloxy group, a C1-10 alkyl group, a C1-10 alkoxyl group, a C3-6 cycloalkyl group, or a C3-6 cycloalkoxy group), or (c) a combination of N-bromosuccinimide and a dialkyl sulfide.