A air filtering apparatus for filtering microorganisms such as virus, bacteria, fungus, etc. contained in air including a mechanism for blowing air to a gas-liquid contact member (5) to or into which electrolytic water achieved by electrolyzing water containing chlorine ions is dropped or infiltrated so that the air is brought into contact with the electrolytic water, and blowing out the filtered air to a room, and a predicting unit (32, 33, 30) for judging pollution of the electrolytic water and predicting adherence of scale to the gas-liquid contact member (5) .