A train communication system that performs communication between a vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) and a vehicle information control apparatus, the train communication system comprising: the vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) to convert a signal to the vehicle information control apparatus into a signal in a network transmission format that is a format used for transmission over a network and transmit the signal via the network, and to convert a signal in the network transmission format received from the vehicle information control apparatus via the network into a signal in an original format; and the vehicle information control apparatus to convert a signal to the vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) into a signal in the network transmission format and transmit the signal via the network, and to convert a signal in the network transmission format received from the vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) via the network into a signal in an original format, characterized in that the vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) comprises an operation unit to output a signal generated by a function of the vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) in which the operation unit is included, and to operate based on a signal input from the vehicle information control apparatus; a serial/parallel conversion unit to convert the signal generated by the operation unit into a serial signal and output the serial signal, and to convert a signal from the vehicle information control apparatus into a parallel signal and output the parallel signal to the operation unit; and a device-side signal conversion unit to convert the serial signal input from the serial/parallel conversion unit into a signal in the network transmission format, and to convert a signal received from the vehicle information control apparatus via the network into a signal in an original format and output the signal to the serial/parallel conversion unit. the vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) to convert a signal to the vehicle information control apparatus into a signal in a network transmission format that is a format used for transmission over a network and transmit the signal via the network, and to convert a signal in the network transmission format received from the vehicle information control apparatus via the network into a signal in an original format; and the vehicle information control apparatus to convert a signal to the vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) into a signal in the network transmission format and transmit the signal via the network, and to convert a signal in the network transmission format received from the vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) via the network into a signal in an original format, characterized in that the vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) comprises an operation unit to output a signal generated by a function of the vehicle-mounted device (20, 30, 40, 50, 60, 70, 80, 90) in which the operation unit is included, and to operate based on a signal input from the vehicle information control apparatus; a serial/parallel conversion unit to convert the signal generated by the operation unit into a serial signal and output the serial signal, and to convert a signal from the vehicle information control apparatus into a parallel signal and output the parallel signal to the operation unit; and a device-side signal conversion unit to convert the serial signal input from the serial/parallel conversion unit into a signal in the network transmission format, and to convert a signal received from the vehicle information control apparatus via the network into a signal in an original format and output the signal to the serial/parallel conversion unit.