1. A navigation system for a vehicle, the system comprising: a displaying means having a display screen; a detecting means for detecting a present position and a heading direction of the vehicle; a storing means for storing road map data for displaying a road map including a road name of a road; a display managing means for reading road map data from the storing means based on the detected present position, and displaying a peripheral road map and a vehicle mark indicating the present position and the heading direction such that the heading direction is shown upwardly in the display screen, wherein the display managing means includes: an angle calculating means for calculating, relative to a travel-estimated road, which is estimated for the vehicle to travel, an intersecting angle of an extending direction of a cross road intersecting with the travel-estimated road at an intersection; a search area designating means for designating a search area shaped of a sector centering on the intersection to include the extending direction of the cross road; an intersecting point retrieving means for retrieving an arc intersecting point between the cross road and an outer circumference arc of the designated search area; and a display position determining means for determining a display position of a road name of the cross road based on a line segment between the intersection and the retrieved arc intersecting point.