PROBLEM TO BE SOLVED: To provide a processing method and a processing unit in which adsorption treatment of an oxo acid compound is effective, temperature control is easy, there is safety, a high volume reduction ratio can be obtained when treating after performing adsorption, and expensive adsorption agents such as a rare earth are not needed to be largely used.SOLUTION: A purification method of radioactive contaminated water or industrial waste water is that an oxo acid compound in the radioactive contaminated water or the industrial waste water is adsorbed to a cerium oxide supported active carbon, thereby the radioactive contaminated water or the industrial waste water is purified, and is characterized in that the oxo acid compound is the oxo acid compound that comprises one of antimony, arsenic, selenium, tellurium, boron and iodine or two or more elements thereof.
