In an embodiment of the present invention, contaminants contained in polycrystalline silicon are removed to obtain highly-pure polycrystalline silicon, with only a small amount of etching. Polycrystalline silicon is washed with use of: a first washing step of bringing fluonitric acid into contact with the polycrystalline silicon; and a second washing step of bringing a non-oxidizing chemical containing hydrofluoric acid into contact with the polycrystalline silicon that has undergone the first washing step.