PURPOSE: To provide a duplicate data update system by which a processing for ensuring the consistency of data on all duplicate data is considerably simplified and by which the complication of the processing does not depend on the number of data bases and duplicate data by updating original data at the time of updating duplicate data in the distributed data base.

CONSTITUTION: When an update request is that from a user in a step 103, original data information is retrieved in a step 105. When it exists, an original data update request is issued in a step 106. When it does not exist, the update processing of self data is executed in a step 107. An extraction data update request is issued to an extraction destination based on data extraction destination information in a step 110. When the update request is not from the user in the step 103, a processing from the step 107 to the step 110 is executed.