A transmitting device includes a parallel data generation unit and a transmitting unit. The parallel data generation unit generates first serial data and second serial data from a data packet, converts the first serial data and second serial data respectively into first parallel data and second parallel data, transmits the first parallel data and second parallel data respectively through first and second parallel transmission paths, and performs the transmission of the first parallel data and the transmission of the second parallel data in parallel. The transmitting unit receives the first parallel data and second parallel data respectively through the first and second parallel transmission paths, re-converts the first parallel data and second parallel data respectively into the first serial data and second serial data, and transmits the first serial data and second serial data to a receiving device respectively through first and second serial transmission paths.