Hexafluoroacetone or a hydrate thereof is produced with a high yield by subjecting a 1-fluoro-4,4-bis(trifluoromethyl)-2,3,5-trioxolanyl ether compound represented by the general formula: wherein R is an alkyl group having 1 to 8 carbon atoms, an aryl group, or a benzyl group, which has been obtained by ozone oxidation of a heptafluoroisobutenyl ether compound, to a reduction reaction in the presence of a reducing agent selected from dialkyl sulfide containing an alkyl group having 3 or 4 carbon atoms, diaryl sulfide, diaryl disulfide, and diaralkyl sulfide.