An autonomous driving operation is performed at an automation level that allows a driver seat passenger to sleep. An approved route approved by the driver seat passenger is acquired. A predetermined delay factor existing on the approved route is detected based on traffic information or weather information. Based on an input signal from a passenger state sensor, it is determined whether the driver seat passenger is asleep. An alternative route that reduces a delay time using map data is searched when detecting the delay factor. A travel plan route is changed to the alternative route without acquiring approval from the driver seat passenger when the alternative route is acquired while the driver seat passenger is asleep.