An image information comparison system is provided that can effectively utilize image information that is captured by an on-board camera for the purposes other than benefiting the vehicle on which the on-board camera is mounted.Image information comparison system 1 has comparison data storage 13 that stores comparison data; on-board camera A, B, C that is mounted on a vehicle, the camera capturing an image that is external to the vehicle; data comparator 14 that compares image information that is captured by on-board camera A, B, C with the comparison data that are stored in the comparison data storage 13 based on biometric authentication technology, character recognition technology or image recognition technology; and reporting means 17 that report a result of comparison made by data comparator 14.