PURPOSE: To readily and economically obtain the objective substance in high selectivity by reacting methylchloroform in the presence of antimony fluorochloride catalyst and a specific amount of tetrachloroethane in fluorinating the methylchloroform with HF and producing the subject substance.

CONSTITUTION: Methylchloroform is reacted with HF at 1:(2.0-2.3) molar ratio in the presence of antimony fluorochloride catalyst and tetrachloroethane (preferably 1,2,2,2-tetrachloroethane) in an amount of 0.2-2.0mol (preferably 0.2-1.5mol) based on 1 mol antimony fluorochloride catalyst at -10 to +20°C to produce the subject substance. The antimony fluorochloride is prepared by reacting, e.g. SbCl5 or a mixture thereof with SbCl3 with HF or further Cl2. The subject substance is useful as a monomer for polymers or a refrigerant, etc., for car coolers.