A vehicle-mounted device (100) has a configuration in which a portable device (10) including a display section (11) is removable. Further, the vehicle-mounted device (100) includes a display section (131) and a control unit (140). The control unit (140) detects that the portable device (10) is mounted or that the portable device (10) is removed and, when detecting that the portable device (10) ismounted, turns off the light of the display section (131). With this, the power consumption of the vehicle-mounted device (100) can be reduced. Further, the case in which the same information is displayed on the display section (131) and the display section (11) is eliminated, thus requiring no processing to synchronize the timings with each other at which the information to be displayed on both the display sections is displayed on the respective display sections.