Provided is an encoding apparatus wherein a transmission data sequence is divided into L short sequences, each of which is then encoded by use of an m-stage pseudo-cyclic low-density parity check encoding system. Each of the L encoded sequences is further divided into shorter sequences, the number of which is identical to the number m of the stages of the pseudo-cyclic codes and each of which has a length m. The shorter sequences are rearranged in order by a replacing module, thereafter encoded, by use of the m-stage pseudo-cyclic low-density parity check encoding system, and outputted. Accordingly, a decoding apparatus with a simple structure where node processing circuits (e.g., minimum-value calculating circuits), the number of which is p that is a submultiple of the number m of the foregoing stages, are provided, can be employed to efficiently decode the codes having a large frame length and a large encoding gain.