A vehicle-mounted device communication controller includes a vehicle-mounted unit for communicating with ID-registered portable units, a switch-detection mechanism for detecting pressing of an operation knob, a switch-operation restriction mechanism for restricting the rotation of the knob, and a door-opening/closure detection mechanism for detecting opening and closure of a door. Signals are exchanged between the vehicle-mounted unit and each portable unit, and a portable unit having succeeded in exchanging the signals is authenticated and released from the restriction. The vehicle-mounted unit includes a sending/receiving part, a controller, an authentication part, and an ID-storage part. When the door-opening/closure detection mechanism detects opening and then closure of the door, the controller performs the search by an all search method, and only when the latest authenticated ID is stored in the ID-storage part, performs the search by an urgent search method using a simple response signal which does not include an ID.