An apparatus for processing an alkaline solution includes a storage tank storing the alkaline solution to be processed; a processing unit sucking a foam phase disposed on the liquid surface level of the alkaline solution in the storage tank, defoaming the foam phase by centrifugal separation, and extracting the foam phase outside the storage tank, the processing unit including an extraction tube; a separating tank separating scum and a liquid, the separating tank being connected to the extraction tube; a scum-discharging component discharging the scum in the separating tank outside the separating tank; and a liquid-discharging component discharging the liquid in the separating tank outside the separating tank. In the apparatus, the scum and the liquid separated in the separating tank are separately discharged outside the separating tank with the scum-discharging component and the liquid-discharging component, respectively.