A water treatment apparatus has a turbidity meter, which is a detection part, for detecting a generation state of bubbles in a micro/nano bubble generation state confirmation tank, as a turbidity of treatment water. The water treatment apparatus also has a controller, which is a control part, for receiving an signal representing the turbidity of treatment water detected by the turbidity meter, to control openings of air flow control valves in an interlocked manner in response to the signal, so that the amount of air flowing through the control valves is automatically controlled. The openings of the air flow control valves are controlled in an interlocked manner by the controller in such a way that the signal representing turbidity shows that the treatment water within the confirmation tank is whitely turbid (i.e., the turbidity shows not less than a specified value).