Method of creating quality grade discrimination criteria for granular material appearance quality grade discrimination device

A method of creating quality grade discrimination criteria in a discrimination device that determines appearance quality grades of granular materials in accordance with the present invention includes a granular material placement step of sorting the granular materials on a per-quality-grade basis and placing the granular materials on an image-capture surface of the image-capturing unit; an imaging data acquisition step of capturing images of the granular materials placed on the image-capture surface by the image-capturing unit and thereby obtaining imaging data; a quality grade information acquisition step of obtaining, on a per-quality-grade basis, pieces of quality grade information on the respective granular materials on the basis of the imaging data; and a quality grade discrimination criteria creation step of creating quality grade discrimination criteria by using the quality grade information obtained on a per-quality-grade basis.