A communication control device used in an on-vehicle communication system including an out-of-vehicle communication device being one of a plurality of function units provided in a vehicle and being capable of communicating with an external device outside the vehicle, and a switching device being capable of relaying communication data from one of the function units to another one of the function units, comprises: an acquisition unit that acquires status information indicating a status of a queue for storing in the switching device at least communication data from the out-of-vehicle communication device; and a control unit that determines restriction of transmission of communication data from the external device to the out-of-vehicle communication device based on the status information acquired by the acquisition unit.