NOVELTY - Method of processing nitrogen-containing organic waste water (1), involves carrying out nitrification process by introducing liquid (nitrogen-containing organic waste water) obtained in denitrification process, circulating (denitrification process) through portion of digestive fluid, which passed through nitrification process, performing solid-liquid separation of digestive fluid using membrane separator and obtaining treated water (6), extracting portion of sludge from denitrification process and/or nitrification process.    USE - For processing nitrogen-containing organic waste water (claimed), for removing nitrogen in the waste water.    ADVANTAGE - The method enables processing nitrogen-containing organic waste water, cost-effectively, and aerobic solid-substance residence time is more easily (than predetermined time) controllable using the sludge densitometer and the removal of nitrogen stabilized without reducing activity of nitrifying bacteria.    DETAILED DESCRIPTION - Method of processing nitrogen-containing organic waste water, involves carrying out denitrification process by introducing nitrogen-containing organic waste water, carrying out nitrification process by introducing liquid obtained in the above step, circulating (denitrification process) through a portion of digestive fluid, which passed through nitrification process, performing solid-liquid separation in the biological nitrogen removal method, using membrane separator, which separates portion of digestive fluid into solid and liquid and obtaining treated water, extracting the portion of sludge from the denitrification process and/or nitrification process, and after performing the solubilization processing, carrying out the denitrification process and/or nitrification process.    An INDEPENDENT CLAIM is included for processing facility of the nitrogen-containing organic waste water.    DESCRIPTION OF DRAWING(S) - The figure shows the schematic flowchart of the processing method. (Drawing includes non-English language text)    Nitrogen-containing organic waste water (1)    Denitrifying tank (2)    Nitrification tank (3)    Circular flow path (4)    Treated water (6)