To always monitor a backward situation, by photographing a rear view mirror and processing the photographed image and displaying a warning to a driver by a warning display means, if necessary, and controlling the warning display means by the driver's response to a moving mechanism controlling means.

A photographed image of a rear view mirror 1 is processed by an image preprocessing means 22 and an image processing means 23 according to the relative speeds and the information is transmitted to a controlling means 23. Next, a driver's direction operation and speed operation to a moving mechanism controlling means 26 are detected by a response detecting means 25 and the controlling means 23 judges if a warning needs to be displayed or not and the level of the warning. If necessary, a control signal is output to a warning display means. The warning display means 24 calls the driver's attention to back side by the direction from the controlling means 23. The warning display means 24 gives vibration to a brake an accelerator, a steering wheel, a clutch and a seat.