A data transmission device comprises a transmitter device and a receiver device. The transmitter device divides a data to be transmitted into an original data requiring protection against code error and a data requiring no protection. The transmitter device then carries out error detection code adding operation and error correction coding at a redundancy 1/N on the original data to generate a coded data. The transmitter device divides the coded data by N, and outputs the N divided coded data and the data requiring no protection on a communication line under a time division multiplexing control. The receiver device receives the N coded data and the data requiring no protection. The receiver device carries out error correction decoding on the N divided coded data and a mixed coded data obtained by mixing the divided coded data, and carries out error detection on decoded data obtained by the decoding. The receiver device then outputs one of the decoded data from which no code error is detected together with the data requiring no protection. The data transmission device can carry out a data transmission protecting the transmitted data from burst code errors and random code errors without increase of redundancy.
