PROBLEM TO BE SOLVED: To provide a processing method for recycling water-absorbing resin powder contained in an absorbent article after using, such as disposed disposable diaper.SOLUTION: A water-absorbing resin processing method includes adding the salt of strong acid and a nitrogen-containing basic compound to a water-absorbing resin powder aggregate made by letting water-absorbing resin powder absorb water to aggregate, followed by mixing. It is all right to add strong acid and a nitrogen-containing basic compound, respectively, instead of adding the salt of strong acid and a nitrogen-containing basic compound. The water-absorbing resin powder is water-absorbing resin powder having acrylic acid as the main component. A water-absorbing resin waste substance processed by the processing method is dried after processing and used as a soil improvement agent or solid fuel.
