1. A method of detecting suspected anomalous shadows, comprising the steps of obtaining a difference image representing the difference between two images, which have been obtained of the same subject at different photographing times, by subjecting said two images to an interimage process to obtain the difference between said two images, obtaining a processed difference image by subjecting the obtained difference image to an image process wherein the actual difference between the two images on which said difference image is based is enhanced relative to the artifacts appearing due to misalignment of the positions of the structuring elements thereof, and detecting the actual difference between the aforementioned two images from the processed difference image as suspected anomalous shadows.