A vehicle-mounted device includes vehicle information detecting unit for detecting an on/off state of vehicle power, relay input/output unit for controlling an external relay configured to make a switch between a starting-disabled state and a starting-enabled state of a vehicle, and vehicle information-associated control unit for controlling the external relay based on a relay control command. The vehicle information-associated control unit controls the external relay based on an elapsed time since a change in the on/off state of vehicle power detected by the vehicle information detecting unit.