The present invention provides a process for the preparation of hexafluoroacetone characterized by bringing hexafluoro-1,2-epoxypropane into contact with at least one catalyst selected from the group consisting of titanium oxide catalysts and fluorinated titanium oxide catalysts to isomerize hexafluoro-1,2-epoxypropane; and a process for the preparation of hexafluoroacetone hydrate characterized by absorbing the hexafluoroacetone prepared by the above process into water to produce crude hexafluoroacetone hydrate, neutralizing the crude hexafluoroacetone hydrate with an alkali, and distilling the resulting mixture. According to the invention, high-purity hexafluoroacetone can be obtained by isomerization of hexafluoro-1,2-epoxypropane with little formation of by-products, and substantially acid-free high-purity hexafluoroacetone hydrate can also be obtained.