Abstract: There is provided a vehicle-mounted communication apparatus and a vehicle-mounted communication system capable of reducing the number of locations where the connectors of communication lines are directly connected in a vehicle. A vehicle-mounted communication apparatus according to the present disclosure includes: a first connection unit, a second connection unit, and a third connection unit to which communication lines provided inside the vehicle are respectively connected; a communication unit configured to perform communication via the communication lines; a first communication path disposed between the first connection unit and the communication unit; a second communication path that directly connects the second connection unit and the third connection unit; and a switching unit for switching the first communication path and the second communication path between a connected state and a cut-off state.