A data transmitting device includes a coded-data generating unit and a data transmitting unit. The coded-data generating unit divides transmission data by a predetermined number in accordance with a data size of the transmission data and then adds a redundant code to the divided transmission data at a predetermined ratio or adds the redundant code to the transmission data at the predetermined ratio so as to generate multiple blocks of coded data. The data transmitting unit groups together the multiple blocks of coded data generated by the coded-data generating unit into a number of blocks that are inserted into a transmission data block, which has a predetermined size, and then transmits the transmission data block.