PURPOSE: To convert perfluoroolefine into an epoxide, by stirring perfluoroolefine under the existence of a correlation moving catalyst in a three-liq. phase system composed of a water phase, an epoxide phase and a reaction phase.

CONSTITUTION: Perfluoroolefine is converted into its epoxide, by being stirred at (-20)-15°C under the existence of the correlation moving catalyst, preferably an org. solvent-soluble quaternary ammonium salt, (e.g. cocobenzyl bis(β- hydroxypropyl) ammonium chloride3), etc., in the three-liq. phase system having a pH of 7.5-9.6. The three liq. phases are aq. soln. (1) sufficiently contg. a metal hypohalogen acid salt, (e.g. sodium hypochlorite), phase (2) contg. the epoxide abundantly, and reaction phase (3) composed of an org. liq., (e.g. toluene), where the distribution coefft. of perfluoroolefine-epoxide is at least 1.3 on the reaction conditions.