A curve-shape modeling device that divides multiple sampling points along a route into a linear section, a relaxation curve section and a steady section, and models a curve shape of the route, includes: a curve extraction unit that extracts a curve from the sampling points based on a curvature of the sampling points; a steady section curvature determination unit that determines a curvature of the steady section based on a curvature of sampling points included in an extracted curve; and a curve entry and exit determination unit that sets a predetermined curvature range including the curvature of the steady section, and determines a start point and an end point of the steady section based on the curvature range.