Abstract: To provide a method for treating floor polish stripping wastewater and washing wastewater that is suitable for treating stripping wastewater produced in stripping with a strongly alkaline stripping agent when a floor polish coating film coated and formed on a floor surface is recoated and for treating washing wastewater produced in surface washing with a floor cleaner having neutral to alkaline properties during periodic or daily washing, this method making it possible to perform operations within a limited interval by treating wastewater within a short time and removing solids, thereby reducing environmental loads. A method for treating stripping wastewater or washing wastewater by which solid-liquid separation process can be performed within a short time and with good efficiency by adding a polyamidine polymer flocculant and converting aggregated particles into nonadhesive flocks of an appropriate size.