An image pickup portion picks up an image of a suspected substance and produces a video signal. Optical fibers transmit the video signal output from the image pickup portion. A video signal processing portion processes the video signals transmitted by the optical fibers and then outputs the processed video signals to a monitor. A trouble detection portion detects trouble in a transmission state of the optical fibers. The video signal processing portion outputs to the monitor only the video signal transmitted by the optical fiber in which the trouble detection portion has not detected trouble.