in fig4 the system comprises an input device 401 where at least one condition of the association rules to be mined is inputted by a user a database converter 402 for preparing database partitions and bit strings an itemset generator 403 for preparing a candidate itemset i e a candidate to constitute the association rule for retrieving database and for counting at least one support count of the candidate itemset and for finding at least one frequent itemset which satisfies the condition of the minimum support inputted by the user a rule generator 404 for generating association rules from the frequent itemset and an output device 405 for outputting the mined association rules a database 406 is connected to the database converter 402 and the itemset generator 403 association rule mining procedure is shown in the block diagram of fig1 first in the input device 401 conditions set for the association rule to be mined as inputted by the user is acquired according to the present invention three types of conditions are acquired as the conditions for the association rule a minimum support a minimum confidence and a minimum confidence increment in the present embodiment the minimum support is set to 25 the minimum confidence is set to 80 and minimum confidence increment.