A decoding device includes: a BP decoder that performs BP decoding on an input signal: a maximum likelihood decoder that performs maximum likelihood decoding on a signal subjected to the BP decoding; and a selector that selects one of the input signal, the signal subjected to the BP decoding, and a signal subjected to the maximum likelihood decoding. In a configuration of the decoding device, when a decoder is appropriately operated according to quality of data, a calculation scale can be reduced, and power consumption can be decreased.