A road shape estimating device has a data obtaining processing unit for obtaining interpolation point data for a plurality of shape interpolation points which represent a shape of a road, a radius calculation processing unit for calculating a radius of curvature at each of shape interpolation points based on the interpolation point data, a corner detection processing unit detecting a corner based on the calculated radius of curvature, and a corner dividing processing unit for obtaining segment lengths of segments between respective shape interpolation points in the corner and dividing the corner by a segment length equal to or larger than a threshold which is set corresponding to an average value of the respective segment lengths.