Abstract: Provided is a processing method for an object, including the steps of: arranging an object in a first portion that is a portion having a space and configured to process the object; and decomposing an organic substance in the object by covering the object with catalysts formed of granules made of a metal oxide containing titanium and bringing the catalysts into contact with the organic substance, and simultaneously maintaining the catalysts in the first portion at a temperature of 480° C. or more and 550° C. or less. The step of decomposing the organic substance in the object includes causing gas containing oxygen to flow into the first portion so that a decomposition reaction of the organic substance occurs, and the catalysts are slightly moved in at least a part of a surface of the object.