To provide a process for producing anhydrous hexafluoroacetone from hexafluoroacetone hydrate. To provide a process taking environment into consideration, that does not require a treatment of wastes, such as waste sulfuric acid, containing organic substances, which is inevitable in processes conducted hitherto using concentrated sulfuric acid, fuming sulfuric acid, and the like.A process for dehydrating a hexafluoroacetone hydrate, comprising introducing a hexafluoroacetone hydrate and hydrogen fluoride either as a mixture or separately into a distillation column, obtaining a composition containing hexafluoroacetone or a hexafluoroacetone-hydrogen fluoride adduct and hydrogen fluoride as a low boiling component, and obtaining a composition containing water and hydrogen fluoride as a high boiling component.