When a predetermined number of pieces of data are retrieved, a retrieving process is performed first on a local database 7 in a LAN 1, and a response counter 8 counts the number of pieces of response data accumulated in a response accumulation device 9. When it is determined that the predetermined number of pieces of response data cannot be obtained from the local database, a remote database 3 is searched by a retrieval device 6 through a communications device 2. Therefore, requests to search unnecessary databases can be reduced, and the load on a network and the remote database 3 can also be reduced successfully.