In a process for treatment of powdery fumed silica, fumed silica to be discarded is collected by dispersing the fumed silica in water. Disclosed is a method for treatment of a fumed silica-containing wastewater collected in the process. The method comprises the steps of: adding an inorganic coagulant containing a metal to a fumed silica-containing wastewater in an amount of 15 to 300 mg/l. in terms of the metal, wherein the wastewater is either a wastewater containing fumed silica at a concentration of 0.05 to 3.0% by mass or a wastewater whose fumed silica content is adjusted to 0.05 to 3.0% by mass; and adding an organic polymeric coagulant to the mixture.