The disclosed image processing system detects the position and speed of a vehicle with high accuracy by accurately measuring the orientation of a rotatable surveillance camera 3 by means of image processing. This system allows mode setting to be switched between an automatic monitoring mode and a manual operation mode. When the mode is switched from the manual operation mode to the automatic monitoring mode, an image processing apparatus 7 recognizes on a screen a plurality of reference points 11 whose locations on a road are given, calculates orientation parameters of the surveillance camera 3 based on the positions of the reference points on the screen, and detects the position and speed of the vehicle based on photographed images of the vehicle using the orientation parameters, thereby detecting phenomena such as traffic congestion and accidents.