NOVELTY - A processing apparatus (100) of nitrogen-having organic waste (110) has aeration processing unit (A), return line (130) and methane-fermentation tank (102) having stir-mixing portions (121) separated by dividing wall (120). Tank (102) performs methane fermentation of waste. Unit (A) carries out aeration processing of fermented material. Process liquid flowing down moves from down to upstream.    USE - For processing of nitrogen-containing organic waste, such as organic refuse.    ADVANTAGE - The processing apparatus of nitrogen-containing organic waste is compact and economical. The disposal of waste from processing apparatus is reduced. The monitoring and controlling of reaction state in the tank is directly enabled.    DETAILED DESCRIPTION - A processing apparatus of nitrogen-containing organic waste has an aeration processing unit, a return line, and a methane-fermentation tank having at least two stir-mixing portions separated by a dividing wall. The methane-fermentation tank carries out methane fermentation of nitrogen-containing organic waste. The aeration processing unit carries out aeration processing of methane-fermented material from methane-fermentation tank. The return line returns one or whole portion of the aeration processed liquid from aeration processing unit to methane-fermentation tank. The processed liquid flowing down between each stir-mixing portion moves from down stream to upstream by plug flow.    An INDEPENDENT CLAIM is included for processing of nitrogen-containing organic waste. Methane fermentation of nitrogen-containing organic waste is carried out in the presence of a methane bacterium, and methane and methane-fermented material are obtained. Gas containing oxygen is blown in methane-fermented material, and aeration processing is carried out. One or whole portion of methane-fermented material after aeration processing is returned to methane-fermentation. The ratio of organic substance load/nitrate-nitrogen load is 4 or more as a service condition in methane-fermentation process. The nitrate-nitrogen concentration of processed nitrogen-containing organic waste is 3000 or less mgN/L.    DESCRIPTION OF DRAWING(S) - The figure shows the outline block diagram of methane-fermentation tank of processing apparatus of nitrogen-containing organic waste based material. (Drawing includes non-English language text).    Nitrogen-containing organic-waste processing apparatus (100)    Methane-fermentation tank (102)    Nitrogen-containing organic waste (110)    Aeration processed liquid (112)    Dividing wall (120)    Stir-mixing portion (121)    Return piping line (130)