A method for producing a high purity of perfluoroethane from hydrofluoroethane (C.sub.2 F.sub.x H.sub.y 1.ltoreq.x, 1.ltoreq.y.ltoreq.5, x+y=6). Cobalt difluoride (CoF.sub.2) as a catalyst is activated into cobalt trifluoride (CoF.sub.3) as a result of the contact reaction with fluorine gas in a reactor. The reactor is purged by removing the fluorine gas remaining in the reactor. The remaining gas is allowed to react with sulfur to give sulfur hexafluoride (SF.sub.6) which is then removed. The hydrofluoroethane is converted into perfluoroethane as a result of the catalyst of the activated cobalt trifluoride at 300-350.degree. C. The feedstock is safer and less corrosive than triple bond-containing compounds such as acetylene. In the method of the present invention, the formation of CF.sub.4 is extremely restrained and no inert gases are employed, so that a very high purity of C.sub.2 F.sub.6 can be obtained at a high conversion rate.