Provided are a data transmission apparatus and a method for the data transmission apparatus to transmit a plurality of packets constituting transmission data to a receiving end. The data transmission apparatus for transmitting a plurality of packets constituting transmission data to a receiving end includes a packet-specific weight calculator configured to calculate packet-specific weights of respective transmission-scheduled original packets at a current time point among the plurality of packets, a packet converter configured to generate one or more error recovery packets from the original packets according to the calculated packet-specific weights, and a transmitter configured to transmit the error recovery packets to the receiving end using a plurality of sessions capable of transmission.