To calculate the radius of curvature calculating based on the values obtained by a plurality of methods and also considering the reliability of the calculated values as a whole integrating the values obtained above.

This apparatus is provided with an image pickup means A for recognizing section lines of the running course, a road data means C, a detection means D for detecting the turning state of own vehicle, a receiving means E of a GPS satellite, a first radius of curvature calculating means F for determining the radius of curvature of the running course based on the results of image pickup by the image pickup means A, a section line recognition state judging means G to judge the recognition state of the running course section lines by the image pickup means A, a second radius of curvature calculating means H to calculate the radius of curvature of the running course according to road data, a reception state judging means I to judge the propriety of the reception state of the receiving means E, a third radius of curvature calculating means J for estimating the radius of curvature of the running course, based on the results of detection by the detection means D and a fourth radius of curvature calculating means K for calculating the radius of curvature integrated data P of the running route by combining the first, second and third radius of curvature calculating means F, H and J with the results of the outputs of the section line recognition state judging means G and the reception state judging means I.