PURPOSE: To instantaneously show a screen where the situation of an illegally intruded part is displayed without requiring the switching of the screen of a CRT image display device when an illegal intrusion occurs in a building, etc.

CONSTITUTION: A screen processing part 5 selectively receives the video signals sent from the burglar monitoring cameras 4a-4b designated by the given camera selecting signal. Then the part 5 synthesizes these received video signals with the image signals of the screen shown on a CRT image display device 6 and outputs the synthetic screen image signals to the device 6. A camera selecting part 2 receives the alarm signal outputted from a burglar system 1 and outputs the camera selecting signals to the part 5 for selection of the cameras 4a-4b.