An anomalous shadow detection system capable of obtaining stable detection capacity across all facilities into which the system is introduced, regardless of variations in the conditions of the image obtaining environments of each facility is provided. An image obtaining means obtains an image of a standard-phantom, and an image readout means obtains phantom-image data thereof. Said phantom-image data is input to an evaluative model detecting means which detects evaluative models contained within the image of the standard-phantom. An evaluating means compares the detected evaluative models to a desired detection level. If the detected evaluative models are of a different detection level than the desired detection level, a parameter setting means resets the detection parameter, depending on the result obtained by the evaluating means 32, and the above processing of the phantom-image data is repeated until the detection result and the desired detection level are the same.