The present disclosure provides a decoding device. The decoding device includes an iteration number computing unit and a recursive decoder. The iteration number computing unit receives multiple packet parameters corresponding to a packet and computes a codeword-number-per-symbol according to packet parameters, in which the packet includes multiple symbols. The iteration number computing unit computes an iteration number according to the codeword-number-per-symbol. The recursive decoder is coupled to the iteration number computing unit, and performs a decoding operation on a codeword within a data field of the packet according to the iteration number.