A technique for detecting an abnormal behavior by monitoring moving objects such as human being and a car. The place where the abnormal behavior of the moving objects occurs is deduced from the position of the moving object and the direction in which the moving object moves and presented to the car. An abnormal detector comprises means for determining the position of the moving object and the direction in which the moving object moves, means for determining the place where an abnormal incident causing an abnormal behavior of the moving object occurs on the basis of the determined position and direction, and means for displaying the place where the abnormal incident occurs. Therefore it is possible to immediately know the cause of the abnormal behavior of the moving object from the video information collected by observation monitoring moving objects such as a human being and a car.