A plurality of servers are each coupled to a different one of a plurality of databases that are synchronized with each other. A search request specifying a search range is sent from a search-requesting device to the servers. Each server calculates a search subrange from the search range specified in the search request received from the search-requesting device, performs a data search operation only within the calculated search subrange of the database coupled thereto, and sends a search result back to the search-requesting device.