1. A differing region detection system, comprising: at least one memory operable to store program instructions; at least one processor operable to read the stored program instructions; and according to the stored program instructions, the at least one processor is configured to be operated as: a difference information generating unit configured to generate inter-image difference information indicating a difference in feature amounts for each sub region between a first image and a second image that has been judged to have identity with the first image, based on a first feature amount vector that is a set of feature amounts respectively corresponding to a plurality of subregions in the first image and a second feature amount vector that is a set of feature amounts respectively corresponding to a plurality of subregions in the second image; a differing region detecting unit configured to detect a differing region that is an image region that differs between the first image and the second image, based on differences in the respective subregions indicated by the inter-image difference information, and output detection information indicating a result of the detection; and a detection result output unit configured to identifiably display a position of the differing region between the first image and the second image based on the detection information; wherein the subregions include at least one split region, and the differing region detecting unit is further configured to detect the differing region with the split region as a unit by allocating a difference value in accordance with the difference to each split region in each sub region based on the inter-image difference information.