An image diagnosis supporting device operates, through digitizing, to apply predetermined image processing to a medical image and to generate a multi-valued image having discrete multiple values. At least one decision making processing routine is then executed on the multi-valued image and/or the medical image; and, from among shadows in the processed image, a focus candidate shadow which is likely to indicate a diseased site is extracted. The extracted focus candidate shadow is then displayed in the medical image so that it is easily identifiable.