There is provided a suspicious behavior detection system capable of specifying and identifying a suspicious person exhibiting abnormal behavior. A suspicious behavior detection system is a system to detect suspicious behavior of a monitored subject, by using images captured by a stereo camera. The suspicious behavior detection system has an ambulatory path acquisition unit which acquires ambulatory path information of the monitored subject, and a behavioral identification unit which identifies behavior of the monitored subject based on the ambulatory path information, and automatically determines suspicious behavior of the monitored subject.