To provide an LDPC decoder, to which SPA is applied, and a method wherein decoding characteristics are improved by reducing the ratio of a message from a check node within messages sent to the same check node. In a decoding device that decodes a received LDPC code by repeating the passing of messages between a plurality of check nodes and a plurality of bit nodes corresponding to a check matrix in each iteration, the order of message computation at a cluster in an iteration out of at least two iterations that have a before-and-after relationship in time and the order of message computation at a cluster in another iteration are varied.