A decoding device has a buffer configured in memory to store N code streams and N decoders connected in series. Each of N decoders decodes a corresponding code steam and sequentially generates partial symbols of M bit width each unit cycle. Among the N decoders, i (i>=2) stage decoders stores multiple probabilistic models in the memory. In each unit cycle, the decoder receives an input of i−1 partial symbols which contains partial symbols generated by the i−1 stage decoder in the former unit cycle, selects one probabilistic model among the multiple probabilistic models based on i−1 partial symbols which are entered previously, generates one partial symbol using previously selected probabilistic models, and outputs the previously generated one partial symbol along with previously entered i−1 partial symbols.