In a header decompression apparatus 709, a header decompressor 703 refers to reference information stored in a reference information manager 707 to decompress a compressed header of a packet received by a packet receiver 704. An error detector 702 detects a CRC error in the packet with its header decompressed by the packet receiver 704, and outputs only a correct packet. A successive error counter 705 counts the number of successive errors detected by the error detector 702. A successive decompression success counter 706 counts the number of decompression successes that successively appear. By referring to these counted numbers, an update request unit 708 transmits an update request to a transmitting side as required. A reference information manager 707 manages the reference information for header decompression. With this structure, the header decompression apparatus can request update of the reference information based on the state of the error.