A technique by which various types of organic waste can be easily treated so as to obtain a reusable material. An apparatus is provided which comprises a vessel (20) for introducing organic waste (18) therein, the vessel being equipped with: stirring means (82), (92), and (98) for stirring the organic waste (18); steam supply means (62), (64), and (66) which supply high-temperature high-pressure steam to the vessel (20); evacuation means (77), (78), and (80) which evacuate the vessel (20); and heating means (24), (68), (64), and (66) which heat the organic waste (18) present in the vessel (20). The apparatus has such constitution, in which the organic waste (18) in the vessel (20) is decomposed by hydrolysis and pyrolysis and vacuum dried using those means.