PURPOSE: To properly and accurately monitor an invader into a room by making a first image pickup device to constantly pickup the image of the whole room with a fixed visual field to obtain respective area/time positions of the image of a moving object and making a second image pickup device to track it by zooming in the direction of expansion with a magnification based on a moving object image area.

CONSTITUTION: The first camera 1 constantly picks-up the image of the whole room 8 with the fixed visual field and the second camera 2 is started based on the detection of the existence of the invader 9 to image-pick-up by catching an expanded image corresponding to the visual field with the invader 9 in the center and tracking the movement of the invader 9. An operation circuit 3 executes the detection of the invader, the decision of the magnification for the image expansion and a command concerning tracking based on the video signal of the first camera 1. The detection of the entering the room concerning the moving object is image-processed by subtracting the image of only the room, which is previously and primarily picked-up, from respective images picked-up by the first camera 1 along with the passing of time. Furthermore, the first camera 1 is set to be a infrared ray passive type and the second camera is set to be a dark vision type, otherwise, both cameras 1 and 2 are set to be the dark vision type.