A data transmission system includes a packet missing state data storage unit that stores packet missing state data including distribution of the numbers of consecutive missed packets in a decoder and distribution of intervals of the packet missing in the decoder; an interleave unit determination processing unit that determines, based on the distribution of the numbers of consecutive missed packets, an interleave unit that represents the number of Forward Error Correction (FEC) blocks, wherein the FEC block is a unit for which an FEC packet is generated; an FEC block determination processing unit that determines, based on the distribution of the intervals of the packet missing, the number of data packets included in the FEC block; and a packet communication processing unit that identifies, based on the determined interleave pattern data, a transmission order of the packets to the decoder.