A prism for reflecting rays of light 17L and 17R incident from left and right image pick-up directions on the rear side of the direction of travel A is disposed in parallel to the vertical direction of a vehicle. The image pick-up optical axis of an image pick-up unit 15 is set to tilt vertically and obliquely with respect to a horizontal plane C, whereby the images in the respective image pick-up directions which are obliquely above or below the horizontal plane are picked up by the image pick-up unit 15.