A technique is provided for efficiently process three-dimensional point cloud position data that are obtained at different viewpoints. A projecting plane is set in a measurement space as a parameter for characterizing a target plane contained in plural planes that form an object. The target plane and other planes are projected on the projecting plane. Then, a distance between each plane and the projecting plane is calculated at each grid point on the projecting plane, and the calculated matrix data is used as a range image that characterizes the target plane. The range image is also formed with respect to the other planes and with respect to planes that are viewed from another viewpoint. The range images of the two viewpoints are compared, and a pair of the planes having the smallest difference between the range images thereof is identified as matching planes between the two viewpoints.