Abstract: A vehicle communication system includes a gateway device. The gateway device is configured to receive electric power from a battery of a vehicle, relay communication among multiple communication lines coupled to respective electronic control units, perform, when receiving a signal through any of the communication lines, a sleep wake-up operation by transmitting a wake-up request signal to switch one or more of the electronic control units to be woken up from a sleep mode to a wake-up mode, and refrain from transmitting the wake-up request signal in a case where the gateway device determines in view of electric power consumption of the battery that transmission of the wake-up request signal is unacceptable.