WATER TREATMENT APPARATUS AND WATER TREATMENT METHOD

A water treatment apparatus according to the present invention includes: ozone injecting equipment that injects ozone gas into a treatment tank into which water to be treated is introduced and stored; a measuring unit that, using at least a first wavelength, measures the spectral light intensity of the water to be treated at a plurality of points in the treatment tank; and a controller that estimates the residual ratio of the spectral light intensity of the first wavelength for treated water that has been ozonated in the treatment tank or for both the treated water and the water to be treated, on the basis of the measurement results measured by the measuring unit at the plurality of points, and controls the rate of ozone injection by the ozone injection equipment using the estimated residual ratio.