An air filtering apparatus for electrolyzing water to generate electrolytic water containing active oxygen species and filtering air by using the electrolytic water, including an air filtering unit having a gas-liquid contact member to which the electrolytic water containing the active oxygen species is circulatively supplied so as to be brought into contact with air, an electrical conductivity detecting unit for detecting the electrical conductivity of water in the air filtering unit, and a water exchange judging unit for judging on the basis of the detected electrical conductivity whether water exchange is necessary or not.