A monitoring area is scanned by an area sensor device (e.g., an optical distance meter) detects objects. Moving objects are identified among the detected objects, and, among the identified moving objects, a moving object which is present in the monitoring area and which has been newest identified is set as a tracking target. The moving object which has been set at the tracking target is automatically tracked by a camera device. As a result, even if there are present a plurality of moving objects in the monitoring area, tracking targets can be switched from one to another, so that it is possible to designate, as a tracking target, a moving object desired by an observer.