Provided is a method for clustering the data point groups of one or more measurement targets located in the same region from among the acquired data point groups. This method is provided with: acquiring a data point group in a region that contains a measurement target from above the measurement target by using a laser scanner; clustering the data point groups that correspond to the top surface of the measurement target as a planar cluster by using a data processing unit; extracting a reference planar cluster which is a reference for making a same-region determination; calculating the difference in height between the reference planar cluster and other planar clusters, and searching for planar clusters exhibiting a height difference within a prescribed threshold; selecting one planar cluster exhibiting a height difference within the prescribed threshold; detecting whether there is overlap between the reference planar cluster and the one planar cluster; and clustering the planar clusters as clusters in the same region when overlap is detected.