An information addition system acquires data and a control signal from a hands-free apparatus and a navigation apparatus. The hands-free apparatus is connected to a mobile communication terminal and includes an address-book data storage unit that associates communication-partner information of the mobile communication terminal with name information and stores the associated information in a personal information database as first personal information. The information addition system includes an additional information acquiring unit that acquires date and time information at an outgoing or incoming call from the navigation apparatus as first additional information and that acquires predetermined information at the outgoing or incoming call as second additional information, and an information adding unit that identifies the first personal information in the personal information database on the basis of the communication-partner information and that associates the first and second additional information with the first personal information and stores the associated additional information.