The invention provides a novel process for producing hexafluoropropylene oxide in higher yield. An organic phase containing hexafluoropropylene (HFP) in an organic solvent and an aqueous phase containing an oxygen-containing oxidizing agent in water are supplied into a microspace preferably together with a phase transfer catalyst.In the microspace, the organic phase comes in contact with the aqueous phase to cause the reaction between hexafluoropropylene (HFP) with the oxygen-containing oxidizing agent preferably by the action of the phase transfer catalyst, thereby producing hexafluoropropylene oxide (HFPO). After the reaction is completed, the organic phase and the aqueous phase are removed from the microspace, thereby obtaining an organic phase containing hexafluoropropylene oxide (HFPO).