1. A prospective abnormal shadow detecting method for detecting a prospective abnormal shadow in a radiation image, characterized by the steps of detecting a primary prospective abnormal shadow in each of at least two radiation images of an object taken in different directions, determining correspondence of positions on the object between the radiation images, and taking, as a final prospective abnormal shadow, only primary prospective abnormal shadows which are detected in the respective radiation images and are in substantially the same position on the object.