PURPOSE: To provide an image monitor device which can detect only a state change in a place at a constant distant from a video camera without detecting a state change nearby the video camera as abnormality even if the state change occurs.

CONSTITUTION: Two video cameras A and B are arranged horizontally in the same direction at a fixed interval. Then, abnormality is detected on the basis of photographed images of both the video cameras A and B and when the abnormality is detected in the both, an abnormality signal K3 is outputted. Consequently, abnormality detected nearby the video cameras A and B is not detected and only abnormality at a point which is more than a certain distance away from the cameras can be detected.