There is provided a process for producing hexafluoropropylene oxide which is novel and capable of achieving a higher yield. An organic phase comprising hexafluoropropylene (HFP) in an organic solvent and an aqueous phase comprising an oxygen-containing oxidizing agent in water are supplied to a small space (or microspace), preferably together with a phase transfer catalyst. The organic phase and the aqueous phase are contacted with each other in the small space, thereby reacting hexafluoropropylene (HFP) with the oxygen-containing oxidizing agent, preferably by an action of the phase transfer catalyst to give hexafluoropropylene oxide (HFPO). After the reaction, the organic phase and the aqueous phase are taken out from the small space to obtain an organic phase comprising the hexafluoropropylene oxide (HFPO).