Processing system and processing method for nitrogen-containing organic waste water

The invention provides a processing system for nitrogen-containing organic waste water: having an autotrophic denitrifying device (30) that denitrifies water to be treated that contains suspended organic matter , soluble organic matter, and ammonia, by performing nitrification, whereby ammonia is oxidated into nitrous acid by autotrophic microbes under aerobic conditions, and anaerobic ammonia oxidation using autotrophic microbes under anaerobic conditions; comprising, in the stage before the autotrophic denitrifying device (30), a suspended organic matter separation device (10) that separates suspended organic matter from the water to be treated, and a soluble organic matter decomposition device (20) that biologically decomposes soluble organic matter contained in the water to be treated having the suspended organic matter separated therefrom; and capable of efficiently performing anaerobic ammonia oxidation by supplying to the autotrophic denitrifying device (30) water to be treated which has reduced suspended organic matter and reduced soluble organic matter therein.