Abstract: A synchronization system and method for databases by which the immediacy of synchronization between the databases can be assured without dialup connection and the power supply to an information terminal need not always be on to keep the information terminal in a standby state is disclosed. The database synchronization system synchronizes data of databases of an application server and an information terminal connected to each other through a network. A first database information update notification section provided in the application server extracts only differential information of the database of the application server and issues a notification of the differential information to the information terminal. A second database information update notification section provided in the information terminal extracts only differential information of the database of the information terminal and issues a notification of the differential information to the application server.