NOVELTY - A nitrogen-containing waste water treatment equipment has initial stage nitrification-denitrification part and latter stage nitrification-denitrification part equipped with organic waste water processor, upstream anaerobic processing tank and downstream aerobic processing tank in each nitrification-denitrification parts, solid-liquid separation tank positioned downstream the latter stage nitrification-denitrification part, and return path which returns thickened sludge to the initial stage nitrification-denitrification part from the solid-liquid separation tank.    USE - A nitrogen-containing waste water treatment equipment.    ADVANTAGE - Energy required in order to produce a fluid circulating flow is reduced, installation cost is reduced by avoiding use of large sized pump, and sludge activity in the initial stage nitrification-denitrification part is raised.    DETAILED DESCRIPTION - A nitrogen-containing waste water treatment equipment has initial stage nitrification-denitrification part and latter stage nitrification-denitrification part equipped with organic waste water processor arranged in series, upstream anaerobic processing tank and downstream aerobic processing tank arranged in series in each nitrification-denitrification parts, solid-liquid separation tank positioned downstream the latter stage nitrification-denitrification part, and return path which returns thickened sludge to the initial stage nitrification-denitrification part from the solid-liquid separation tank. The initial stage nitrification-denitrification part has 1st raw water feed route which supplies 1st nitrogen-containing waste water to anaerobic processing tank, and 1st circulation path which supplies the liquid mixture in the tank to anaerobic processing tank from the aerobic processing tank. The latter stage nitrification-denitrification part has 2nd raw water feed route, where the supplied water quantity is larger than 1st nitrogen-containing waste water, and supplies 2nd nitrogen-containing waste water with nitrogen concentration lower than 1st nitrogen-containing waste water to anaerobic processing tank, and 2nd circulation path which supplies the liquid mixture in the tank to an anaerobic processing tank from aerobic processing tank. An INDEPENDENT CLAIM is included for nitrogen-containing waste water treatment method.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the nitrification-denitrification processing apparatus.    Organic waste water processor (10)    Initial stage nitrification-denitrification part (20)    Anaerobic tanks (21, 22)    Aerobic tank (23)    Latter stage nitrification-denitrification part (30)