1. A three-dimensional modeling apparatus comprising: an image obtaining section that obtains image sets picked up by a stereoscopic camera; a generating section that generates three-dimensional models of an object based on each of the obtained image sets; a three-dimensional model selecting section that selects a first three-dimensional model and a second three-dimensional model to be superimposed on the first three-dimensional model among the generated three-dimensional models; an extracting section which extracts first feature points from the selected first three-dimensional model and second feature points from the selected second three-dimensional model; a feature-point selecting section that selects feature points having a closer distance to the stereoscopic camera from the extracted first feature points and the extracted second feature points, respectively; a parameter obtaining section that obtains a transformation parameter for transforming a coordinate of the second three-dimensional model into a coordinate in a coordinate system of the first three-dimensional model based on the selected first and second feature points; a transforming section that transforms the coordinate of the second three-dimensional model into the coordinate in the coordinate system of the first three-dimensional model using the transformation parameter; and a superimposing section that superimposes the second three-dimensional model having a transformed coordinate on the first three-dimensional model, wherein the feature-point selecting section (i) performs clustering on the extracted first and second feature points to create two clusters based on a distance from the stereoscopic camera, and (ii) selects the first feature point and the second feature point belonging to respective clusters having the closer distance to the stereoscopic camera.