To prevent erroneous detection of a hand in a region except for an operating portion by setting each of detection areas of an optical area sensors vertical by crossing them in front of the operating portion and detecting the hand of an operator approaching the front of the operating portion from a logical product of each output of the sensors input to a logical circuit.

A light receiving axis is set to cross each of detection areas of two optical area sensors 3, 4 with each other in front of an operating portion. When a hand of an operator approaches a common detection area, both of the sensors 3, 4 detect the hand and both of them output a '1' level signal. Thereafter, levels of input ends 54, 55 of an AND gate 51 are made the '1' level, a level of an output end 56 of the gate 51 is reversed to the '1' level, and a detection signal is output from a logical circuit 5. A controller 8 starts an inter-vehicle distance detection device by receiving this signal and automatically detects a distance with a forward travelling vehicle. Consequently, it is possible to prevent a rear-end collision due to forward carelessness even when a line of sight is directed to the operating portion.