An administration management system for managing vehicles includes plural vehicle units and plural cellular phones respectively having common codes for correspondence between vehicle units and cellular phones. When the common code matches, the vehicle unit and the cellular phone perform an automatic connection procedure and administration management information acquired by the vehicle unit is transmitted to a center unit through a broad range network from the cellular phone. The cellular phone and the vehicle unit are prevented from being connected with each other in an erroneous manner without undergoing complicated connection procedure so as to establish appropriate communication for transmission of administration management information by using the common code assigned thereto.