The present invention provides a novel method for separating hexafluoropropylene oxide (HFPO) from hexafluoropropylene (HFP), which is capable of reducing the burden on the environment. A mixture including HFPO and HFP is subjected to an extractive distillation operation using, as a solvent, at least one of a fluorine-containing saturated compound represented by the general formula CnHaFb (wherein n, a and b are integers which satisfy: n=3 to 8, 0≦a≦2n+1, and 1≦b≦2n+2) thereby separating into a first fraction including HFPO and a second fraction including HFP and the solvent. At least one of 1-bromopropane and 2-bromopropane may be u as the solvent in place of the fluorine-containing saturated compound.