PURPOSE: To approximately express a shape in a state that a shape feature of an object shape remains saved by the specific number of apexes from a measuring point on the surface of an object, in the object approximate expression system for expressing approximately the shape of an object body by using a wire frame model.

CONSTITUTION: This system is provided with a shape feature extracting part 102 for extracting a general feature related to a shape from an inputted measuring point 201 group, an elliptical body model generating part 103 for generating an elliptical body 203 from the general feature related to the shape, an initial model generating part 104 for plotting the apex 204 onto the surface of the elliptical body 203 and generating the initial model of a wire frame model, an adjacent point searching part 105 for searching the measuring point 201 being in the vicinity of the apex 204, a curvature calculating part 106 for calculating a curvature of the measuring point 201, a corresponding point estimating part 107 for estimating the corresponding point 201, a corresponding point estimating part 107 for estimating the corresponding point from the measuring point 201 and its curvature with respect to the apex 204, and a model updating part 108 for moving the apex 204 to the corresponding point and updating the wire frame model.