PURPOSE: To perform highly accurate navigation by calculating a horizontal distance up to an object, and correcting the current position of an own vehicle using the calculated distance, at the time of recognizing the object such as a traffic signal.

CONSTITUTION: The elevation of a traffic signal S recognized with an object recognition means at a point A is assumed to be α, and the elevation thereof is assumed to be β at a point B after travel approaching thereto by a distance L. Provided that a point where a perpendicular from the signal S intersects a horizontal line is taken as a reference point O, a distance between two points O and B is obtained from a relationship between two triangles OAS and OBS as SX=L.tanα/(tanβ-tanα). Also, the distance SX given by the expression is equal to a horizontal distance up to the signal S at the point B and, therefore, an accurate current position can be calculated on the basis of the position of the signal S (or crossing where the signal S is installed) in map information and the horizontal distance SX.