In a navigation system using a bird's-eye view display mode, map data on a plan view map are subjected to a perspective projection conversion to obtain drawing data on a bird's-eye view map. In this case, an input of the position of a view point is accepted, and a projection plane for a bird's-eye view is determined on the basis of the coordinates of a current position and a destination and the position of the view point so that the display positions of the two points which have been subjected to perspective-projection conversion are coincident with predetermined positions. Alternatively, an input of a scale is accepted, and the position of the view point and the projection plane are determined on the basis of the coordinates of the two points and the scale so that the display positions of the two points after the perspective projection conversion are coincident with predetermined positions and the drawing scale is coincident with the input scale. Or, as a further alternative, an input of the projection angle is accepted, and the projection plane is determined on the basis of the projection angle and the position of the view point.