Further, as illustrated in FIG. 17A, an X mark being an attention-calling mark 56′ is displayed at the monitor device 24 as well at a position behind a large-sized vehicle 55′ parking/stopping on a road, so that the occupant is caused to recognize the obstacle being on the scheduled travel course. It is preferable similarly that the attention-calling mark 56′ is displayed in a striking color such as red and orange, and further, is displayed as being blinked.