A navigation system, comprising: a route selecting device for selecting a scheduled route along which a mobile body is scheduled to move towards a destination; and a display device for displaying the scheduled time (Tg) of arrival of the mobile body while the mobile body moves along the scheduled route; characterised by: an acquiring device for acquiring traffic congestion information about traffic congestion along the scheduled route; a searching device for searching for a different route while the mobile body is moving along the scheduled route, the different route avoiding traffic congestion informed to the acquiring device; and the display device being configured to display simultaneously for a given point, the scheduled time (Tg) of arrival at the destination taking the scheduled route and the difference in time between the scheduled time (Tg) of arrival at the destination taking the scheduled route and the scheduled time (To) of arrival at the destination taking the different route in the case where the scheduled time (To) of arrival at the destination taking the different route is less than the scheduled time (Tg) of arrival at the destination taking the scheduled route. a route selecting device for selecting a scheduled route along which a mobile body is scheduled to move towards a destination; and a display device for displaying the scheduled time (Tg) of arrival of the mobile body while the mobile body moves along the scheduled route; characterised by: an acquiring device for acquiring traffic congestion information about traffic congestion along the scheduled route; a searching device for searching for a different route while the mobile body is moving along the scheduled route, the different route avoiding traffic congestion informed to the acquiring device; and the display device being configured to display simultaneously for a given point, the scheduled time (Tg) of arrival at the destination taking the scheduled route and the difference in time between the scheduled time (Tg) of arrival at the destination taking the scheduled route and the scheduled time (To) of arrival at the destination taking the different route in the case where the scheduled time (To) of arrival at the destination taking the different route is less than the scheduled time (Tg) of arrival at the destination taking the scheduled route. an acquiring device for acquiring traffic congestion information about traffic congestion along the scheduled route; a searching device for searching for a different route while the mobile body is moving along the scheduled route, the different route avoiding traffic congestion informed to the acquiring device; and the display device being configured to display simultaneously for a given point, the scheduled time (Tg) of arrival at the destination taking the scheduled route and the difference in time between the scheduled time (Tg) of arrival at the destination taking the scheduled route and the scheduled time (To) of arrival at the destination taking the different route in the case where the scheduled time (To) of arrival at the destination taking the different route is less than the scheduled time (Tg) of arrival at the destination taking the scheduled route.