A method of preparing pentafluoroethane wherein chlorine-containing carbon compounds are fluorinated in the presence of chromium catalysts that are in an amorphous state and wherein the main component is chromium compounds with the addition of at least one metal element selected from the group composed of indium, gallium, cobalt, nickel, zinc and aluminum and the average valence of the chromium in said chromium compounds is not less than +3.5 but not more than +5.0. And said chromium catalysts and a preparation method thereof. A method of preparing pentafluoroethane wherein the total yield of chlorofluoroethane by-products can be decreased without significantly deteriorating the generation activity of the pentafluoroethane and compounds which can be recycled in the reaction system. And to provide catalysts for this fluorination and a preparation method thereof.