A data transmission apparatus for sequentially transmitting data in units of packets each containing transmission data to the receiving end, comprises: a reception unit for receiving the transmission data as an input signal; a packet formation unit for receiving the transmission data received, and forming an uncompressed packet in which predetermined transmission data is stored as uncompressed data, and a compressed packet in which at least a portion of transmission data that follows the predetermined transmission data is compressed and stored as compressed data; a reference information management unit for holding and managing, as reference information, information relating to the uncompressed packet formed by the packet formation unit; and a transmission unit for transmitting the respective packets formed by the packet formation unit, as a transmission signal, to the receiving end. The packet formation unit forms compressed data to be stored in a compressed packet, on the basis of the transmission data of the uncompressed packet and the reference information stored in the reference information management unit. Therefore, the number of packets to be discarded at the receiving end due to an error which has occurred in the radio section is reduced, whereby the quality of data transmitted in the transmission path including the radio section is improved.