The present invention provides an image processing system, which can reduce calculation time by alleviating a calculation load in assessing the occurrence of tampering of an image.For example, the image processing system of the present invention first identifies a type of a form of an image to be assessed in assessing the occurrence of tampering. Next, a characteristic amount of a certain region (flexible region) corresponding to the identified type of a form is extracted as a characteristic amount of the image to be assessed. Then, the extracted characteristic amount of image to be assessed and the characteristic amount extracted from a certain region in an original image are compared and the compared result is notified as the assessment result.A flexible region, to which a user writes, is preferably specified as said certain region.