A decoding device which can efficiently encode/decode spectral data in a high pass section of a broadband signal. In the device, a sample group extraction unit partially selects spectral components by means of an ease of selection importance which is the extent that the spectral components come close to the spectral component having the maximum amplitude value, in the spectrum of a high pass estimated by means of first parameters contained in second encoded information and bands most approximated to each of the spectrums of a plurality of sub-bands calculated from the spectrum of a second decode signal; a logarithmic gain application unit applies second parameters to the partially selected spectral components; and an interpolation processing unit applies third parameters which are adaptively set according to the value of the second parameters, to the spectral components which were not partially selected.