Abstract: A process for purifying 1,1,1,2-tetrafluoroethane which comprises allowing an HF-containing 1,1,1,2-tetrafluoroethane-concentrated fraction to contact at a low temperature with hydrofluoric acid which is an extraction solvent and has an HF concentration equal to or higher than an HF concentration at a water-HF azeotropic point, thereby effecting two-phase separation, and subsequently recovering 1,1,1,2-tetrafluoroethane from the separated lower phase, wherein hydrofluoric acid to be used as the extraction solvent has a concentration of from 38 to 70% by weight, and the extraction and two-phase separation steps are effected at a temperature of from -35.degree. to 35.degree. C. According to the purification process, HF can be recovered economically from a 1,1,1,2-tetrafluoroethane fraction containing a small amount of HF.