An accelerated oxidation treatment method of performing oxidation treatment upon treatment water by supplying ozone and hydrogen peroxide to the treatment water, including an accelerated oxidation treatment process of bringing hydrogen peroxide and ozone into contact with the treatment water, and a bromate ion concentration measurement process of measuring the bromate ion concentration in the treatment water after the accelerated oxidation treatment process, with the amount of hydrogen peroxide supplied in the accelerated oxidation treatment process being adjusted on the basis of the measured value of bromate ion concentration.