To provide a treatment method for incineration ash which changes incineration ash discharged from an incinerator or the like into a reusable material without conducting a removal process for toxic substances such as a heavy metal at an industrial waste disposal site, and to provide a useful material which is generated by the treatment method.

The treatment method for incineration ash contains a diffusing/ mixing process (S1) in which a solidifying material 5 containing an inorganic solidifying material and polyacrylamide modifier is put in incineration ash 6 and diffused and mixed, and a granulation process (S2) in which a mixture 7 produced by diffusion and mixture is granulated by shearing repeatedly.