NOVELTY - A bio-deodorizing system comprises water circulation path (1) where water circulates through inside of system, deodorizing tank (2) which has first carrier which carries microorganisms which carries out nitrification processing of ammonia, denitrifying tank (3) with second carrier which carries microorganisms which perform denitrifying processing, and organic matter supply part (4) which supplies organic matter which makes treated water before processing by deodorizing tank and supplying denitrifying tank.    USE - A bio-deodorizing system for composting plant, sewage works, livestock barn, food processing factory, or organic refuse disposal plant.    ADVANTAGE - The bio-deodorizing system maintains favorable bio-deodorizing effect over a long period of time.    DETAILED DESCRIPTION - A bio-deodorizing system comprises water circulation path (1) where water circulates through inside of system, deodorizing tank (2) where odor gas containing ammonia is supplied and has first carrier which carries microorganisms which carries out nitrification processing of ammonia and converts ammonia into nitrous acid and/or nitric acid, denitrifying tank (3) with second carrier which carries microorganisms which perform denitrifying processing, decompose nitrous acid and/or nitric acid generated in deodorizing tank and converts nitrous acid and/or nitric acid into nitrogen, organic matter supply part (4) which is provided in water circulation path and supplies organic matter which makes treated water before processing by deodorizing tank and supplying denitrifying tank, organic matter removal tank (5) with third carrier which carries microorganisms which decompose organic matter contained in treated water provided in water circulation path, processed by denitrifying tank and discharged from denitrifying tank, and return path (15) which returns treated water after processing by organic matter removal tank to deodorizing tank. The treated water which was processed by deodorizing tank and supplied to denitrifying tank stimulates denitrifying processing in denitrifying tank.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the bio-deodorizing system.    Water circulation path (1)    Deodorizing tank (2)    Denitrifying tank (3)    Organic matter supply part (4)    Organic matter removal tank (5)    Return path (15)