NOVELTY - A control apparatus of biological water treatment apparatus comprises biological reactor (2) which has primary sedimentation basin (1), anaerobic tank (4, 5) and aerobic tank (6) and final sedimentation tank (3) and in which to-be-processed water which flows in and flows out of primary sedimentation basin is stored, amount detection unit of inflow phosphorus which detects amount of phosphorus of to-be-processed water, anaerobic tank influent volume control signal output unit, and anaerobic tank influent volume adjustment unit (11).    USE - A control apparatus of biological water treatment apparatus (claimed).    ADVANTAGE - Denitrification and phosphorus discharge are efficiently performed and favorable water quality is ensured.    DETAILED DESCRIPTION - A control apparatus of biological water treatment apparatus comprises biological reactor (2) which has primary sedimentation basin (1) in which to-be-processed water which flows in from system outside and in which to-be-processed water which flows into primary sedimentation basin mixes with activated sludge which flows out, anaerobic tank (4, 5) and aerobic tank (6) in which liquid mixture of to-be-processed water and activated sludge moves in, and final sedimentation tank (3) in which liquid mixture which flowed out of biological reactor flows in, and in which to-be-processed water which flows in and flows out of primary sedimentation basin is stored, amount detection unit of inflow phosphorus which detects amount of phosphorus of to-be-processed water that flows in into the primary sedimentation basin from system outside, anaerobic tank influent volume control signal output unit which outputs the amount signal of to-be-processed water bypass inflow, and anaerobic tank influent volume adjustment unit (11) which is provided between primary sedimentation basin and anaerobic tank and adjusts the amount of bypass inflow to-be-processed water to anaerobic tank according to output value of anaerobic tank influent volume control signal output unit. Signal is output according to the difference of output value of amount detection unit of inflow phosphorus and reference value.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the control apparatus of biological water treatment apparatus. (Drawing includes non-English language text).    Primary sedimentation basin (1)    Biological reactor (2)    Final sedimentation tank (3)    Anaerobic tank (4, 5)    Aerobic tank (6)    Anaerobic tank influent volume adjustment unit (11)