To analyze a data set having a one-to-many relation, the number of simultaneous occurrences of data in which two data elements are coexistent is obtained for all combinations of two data elements. A dependence ratio of one data element upon the other data element is calculated from the numbers of simultaneous occurrences. The data elements are grouped based upon the numbers of occurrences of individual data elements and the dependence ratios compared with the predetermined thresholds. Based on the number of occurrences of individual data elements and the dependence ratios, subordinate relations of data elements within the same group are specified and displayed to a user in the form of a tree or balloon figure.