Abstract: The present invention relates to an apparatus for treating organic waste including: a first circulation line having a first circulation pump connected thereon so as to supply a portion of the organic waste being acid fermented in an acid fermenter to a methane fermenter; a second circulation line having a second circulation pump connected thereon so as to supply a portion of anaerobic digestive fluid methane fermented in the methane fermenter to the acid fermenter; and vortex generating means having a plurality of first, second and third nozzles disposed in the methane fermenter so as to allow the anaerobic digestive fluid in the methane fermenter to be agitated by vortices generated thereof.