Provided is a method for treating a used absorbent article, this method being hygienic and capable of recovering recyclable material with a high degree of safety. This method for treating a used absorbent article is characterized by including (a) an acidic electrolyzed water treatment step that treats the used absorbent article in a treatment tank that has acidic electrolyzed water serve as a treatment fluid. This method preferably further includes (b) an alkaline electrolyzed water treatment step that treats the used absorbent article in a treatment tank that has alkaline electrolyzed water as a treatment fluid.