A decoding device comprising: demultiplexing means configured to demultiplex input encoded data into low frequency encoded data and an index for obtaining an estimating coefficient used for generation of a high frequency audio signal; 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; feature amount calculating means configured to calculate feature amount that expresses a feature of said encoded data using at least one of said low frequency sub-band signal and said low frequency audio signal; high frequency sub-band power calculating means configured to calculate a high frequency sub-band power of the high frequency sub-band signal of a high frequency sub-band by multiplying said feature amount by said estimating coefficient determined by said index of a plurality of estimating coefficients prepared beforehand regarding each of a plurality of high frequency sub-bands making up the band of said high frequency audio signal, and obtaining a sum of said feature amount by which said estimating coefficient has been multiplied; high frequency signal generating means configured to generate said high frequency audio signal using said high frequency sub-band power and said low frequency sub-band signal; and synthesizing means configured to synthesize the low frequency audio signal generated by the low frequency decoding means and the high frequency audio signal generated by the high frequency signal generating means and to output a synthesized signal. demultiplexing means configured to demultiplex input encoded data into low frequency encoded data and an index for obtaining an estimating coefficient used for generation of a high frequency audio signal; 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; feature amount calculating means configured to calculate feature amount that expresses a feature of said encoded data using at least one of said low frequency sub-band signal and said low frequency audio signal; high frequency sub-band power calculating means configured to calculate a high frequency sub-band power of the high frequency sub-band signal of a high frequency sub-band by multiplying said feature amount by said estimating coefficient determined by said index of a plurality of estimating coefficients prepared beforehand regarding each of a plurality of high frequency sub-bands making up the band of said high frequency audio signal, and obtaining a sum of said feature amount by which said estimating coefficient has been multiplied; high frequency signal generating means configured to generate said high frequency audio signal using said high frequency sub-band power and said low frequency sub-band signal; and synthesizing means configured to synthesize the low frequency audio signal generated by the low frequency decoding means and the high frequency audio signal generated by the high frequency signal generating means and to output a synthesized signal.