A decoding device comprising: demultiplexing means configured to demultiplex input encoded data into at least low frequency encoded data and an index; low frequency decoding means configured to decode said low frequency encoded data to generate a low frequency audio signal; sub-band dividing means configured to divide the band of said low frequency audio signal into a plurality of low frequency sub-bands to generate a low frequency sub-band signal for each of said low frequency sub-bands; and generating means configured to generate a high frequency audio signal based on said index and said low frequency sub-band signal; wherein said index is information indicating a coefficient used for generation of said high frequency signal; and said generating means comprises: feature amount calculating means configured to calculate a feature amount that expresses a feature of said encoded data using said low frequency sub-band signal; high frequency sub-band power calculating means configured to calculate a high frequency sub-band power of a high frequency subband signal of a high frequency sub-band by calculation using said feature amount and said coefficient regarding each of a plurality of high frequency sub-bands making up the band of said high frequency signal; and high frequency signal generating means configured to generate said high frequency audio signal based on said high frequency subband power and said low frequency sub-band signal; wherein said high frequency sub-band power calculating means is configured to calculate said high frequency sub-band power of said high frequency sub-band signal of said high frequency sub-band by linearly combining a plurality of said feature amount using said coefficient prepared for each of said high frequency sub-bands. demultiplexing means configured to demultiplex input encoded data into at least low frequency encoded data and an index; low frequency decoding means configured to decode said low frequency encoded data to generate a low frequency audio signal; sub-band dividing means configured to divide the band of said low frequency audio signal into a plurality of low frequency sub-bands to generate a low frequency sub-band signal for each of said low frequency sub-bands; and generating means configured to generate a high frequency audio signal based on said index and said low frequency sub-band signal; wherein said index is information indicating a coefficient used for generation of said high frequency signal; and said generating means comprises: feature amount calculating means configured to calculate a feature amount that expresses a feature of said encoded data using said low frequency sub-band signal; high frequency sub-band power calculating means configured to calculate a high frequency sub-band power of a high frequency subband signal of a high frequency sub-band by calculation using said feature amount and said coefficient regarding each of a plurality of high frequency sub-bands making up the band of said high frequency signal; and high frequency signal generating means configured to generate said high frequency audio signal based on said high frequency subband power and said low frequency sub-band signal; feature amount calculating means configured to calculate a feature amount that expresses a feature of said encoded data using said low frequency sub-band signal; high frequency sub-band power calculating means configured to calculate a high frequency sub-band power of a high frequency subband signal of a high frequency sub-band by calculation using said feature amount and said coefficient regarding each of a plurality of high frequency sub-bands making up the band of said high frequency signal; and high frequency signal generating means configured to generate said high frequency audio signal based on said high frequency subband power and said low frequency sub-band signal; wherein said high frequency sub-band power calculating means is configured to calculate said high frequency sub-band power of said high frequency sub-band signal of said high frequency sub-band by linearly combining a plurality of said feature amount using said coefficient prepared for each of said high frequency sub-bands.