[Problem] To provide: a division unit in which a reception side can restore, to the original data, data that has been divided and transmitted by a transmission side and received via different transmission lines; a communication device; a communication system; a data division method; and a data division program. [Solution] A data division unit 200 comprising a division part 300. Depending on a plurality of transmission lines that run parallel to each other, the division part 300 divides data into divided data with lengths that correspond to the respective delay times of each of the plurality of transmission lines, and inputs the divided data into a communication tool that transmits transmission data, which is based on the divided data, according to the transmission lines.
