1. A 3D modeling apparatus comprising: an accepting unit configured to accept a plurality of pairs of images that are obtained by capturing an image of a subject multiple times at different angles using a stereo camera that is configured to obtain a pair of images in a single shooting; a generator configured to generate a plurality of 3D models of the subject based on the accepted pairs of images, wherein each of the 3D models corresponds to one of the pairs of images; a selector configured to select a first 3D model and a second 3D model from the plurality of 3D models; an extracting unit configured to extract a plurality of first feature points from the first 3D model and extract a plurality of second feature points from the second 3D model; an acquiring unit configured to (i) select three first feature points from the plurality of first feature points, (ii) select three second feature points from the plurality of second feature points, such that a triangle whose three vertices correspond to the three first feature points is congruent to a triangle whose three vertices correspond to the three second feature points, and acquire coordinate transformation parameters such that positions of the three second feature points coincide with positions of the three first feature points; a transformation unit configured to transform coordinates of the second 3D model into coordinates in a coordinate system of the first 3D model, based on the acquired coordinate transformation parameters; and a combining unit configured to combine the second 3D model having the transformed coordinates on the first 3D model.