Interleave device, interleaving method, deinterleave device, and deinterleave method

An encoder in a data transmission/reception system has a byte interleaver for performing folding interleaving on encoded data ED in units of a byte and a packet interleaver for performing folding interleaving, in units of a packet, on byte interleave data BID generated by this byte interleaver. A decoder has a packet de-interleaver for performing folding de-interleaving, in units of a packet, on packet interleave data PID' and a byte de-interleaver for performing folding de-interleaving, in units of a byte, on byte interleave data BID' generated by this packet de-interleaver. It is thus possible to correct a significant burst error containing a packet loss even with an error correction code having a very small code length.