An efficient extraction of a meaningful frequent itemsets. The present invention discloses a system that includes a decision unit that decides a new itemset that becomes an investigation target in the same sequence as searching an itemset tree in a depth-first manner and in descending order. The present invention further discloses a frequent occurrence determining unit that registers the frequency of occurrence of the new itemset in a table if the frequency of occurrence is equal to or more than a predetermined threshold. The present invention includes a correlation determining unit that determines whether there is a correlation between each item in the new itemset and a subset of remaining items that were removed from the new itemset. The present invention discloses a registration unit that registers the new itemset in a set of meaningful frequent itemsets if the determination is positive for all items of the new itemset.