In a case where application data stored in a PC database 300a are edited by a PC 300, and the edited contents are to be reflected to contents of the memory of a terminal database 200a, PC 300 refers to a synchronization profile SP including item IDs and ID numbers of a most recent synchronization communication and communication time information of the synchronization communication, thereby detecting which items have been edited at a time subsequent to completion of a most recent synchronization communication.