Further, at the behavior display area 35a of the monitor device 24, a virtual vehicle of the own vehicle that performs lane change is displayed as a moving image of a virtual image 46″. The virtual image 46″ is displayed so that the virtual vehicle of the own vehicle travels on the arrow of the symbol image 44″ indicating the travel course for lane change as having the arrow as the trajectory therefor. Similarly to FIGS. 13A to 13D, FIGS. 14A to 14C illustrate, in the order of time passage, a transition of that the virtual image 46″ of the own vehicle performs lane change on the display screen of the monitor device 24.