NOVELTY - A water treatment apparatus (10) comprises water-treatment tank consists of aerobic tank (11, 32, 42) which performs organic matter decomposition and nitrification and anaerobic tank (12, 31, 41) for denitrification and are connected in series, wherein organic substance and nitrogen which flow to-be-processed water to water-treatment tank and are contained in to-be-processed water are removed, and support escape prevention unit (17) provided in each water-treatment tank to prevent support from flowing out of water-treatment tank while support for immobilizing microorganisms is injected.    USE - A water treatment apparatus for wastewater.    ADVANTAGE - Microorganisms are made to exist in water-treatment tank with high density, malfunctions are avoided, water treatment of to-be-processed water is performed stably with high process efficiency without wearing out support over a long period of time, and operation cost of water treatment is reduced.    DETAILED DESCRIPTION - A water treatment apparatus (10) comprises water-treatment tank consists of aerobic tank (11, 32, 42) which performs organic matter decomposition and nitrification and anaerobic tank (12, 31, 41) for denitrification and are connected in series, wherein organic substance and nitrogen which flow to-be-processed water to water-treatment tank and are contained in to-be-processed water are removed, support escape prevention unit (17) provided in each water-treatment tank to prevent support from flowing out of water-treatment tank while support for immobilizing microorganisms is injected, aeration apparatus (21) equipped in aerobic tank, and stirring apparatus (18) equipped in anaerobic tanks and forms and stirs water flow by ejecting to-be-processed water.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of a water treatment apparatus. (Drawing includes non-English language text).    Water treatment apparatus (10)    Aerobic tank (11, 32, 42)    Anaerobic tank (12, 31, 41)    Support escape prevention unit (17)    Stirring apparatus (18)