To reduce the interior noise by the operating sound of a DC-ROM drive or cooling fan at the time of non-navigation display.

This system comprises a key input processing part 9 for detecting the nonuse of navigation display function and a power source control part 13 for stopping, when the nonuse of navigation display function is detected, the operations of a CD-ROM drive 5 that is the reading means of map matching data used in autonomous navigation means and a cooling fan 7. When the navigation display is not performed, only position measurement by GPS is performed without performing map matching data processing, whereby the noise accompanying the access to the DC-ROM drive 5 or the noise accompanying the operation of the cooling fan 7 can be eliminated.