1. A volume data analysis system comprising: a modality for receiving a measured signal acquired by scanning a measuring object and generating three-dimensional volume data; an input device for inputting information in response to manipulation; a controller for processing the three-dimensional volume data generated by the modality and the information input from the input device; and a display device for displaying a processing result of the controller; wherein the controller includes: a cluster generator for polygonizing and converting the three-dimensional volume data generated by the modality into polygon data and dividing the converted polygon data into a plurality of clusters; a feature vector calculation unit for calculating an L2 norm vector of spherical harmonics as a feature vector with respect to each of the clusters based on the polygon data constituting the each cluster; an identification unit for identifying whether each cluster is a target or not, based on each feature vector calculated by the feature vector calculation unit and learning data acquired by machine learning by using training data; and an image generator for generating an image of a cluster identified as the target by the identification unit among each of the clusters generated by the cluster generator, from the polygon data constituting the relevant each cluster and having the display device display at least the generated image.