Further, a virtual vehicle of the own vehicle that performs lane change is displayed as well at the monitor device 24 as a moving image of a virtual image 54′. The virtual image 54′ is displayed so as to travel on the arrow of the symbol image 53′ indicating the travel course for lane change as having the arrow as the trajectory therefor. The virtual image 54′ is displayed as well, for example, as being entirely translucent in while or a light color to the extent that at least outline of the own vehicle is recognizable so as to prevent misrecognition and confusion with an actual vehicle for the occupant.