A decoding apparatus comprising: a decoding part decoding a spectrum code which is a spectrum code for each frame in a predetermined time section and in which bits are not assigned to a part of a high side, to obtain a frequency-domain sample sequence; a bandwidth extending part obtaining a decoded extended frequency spectrum sequence by arranging samples based on K samples, K is an integer equal to or larger than 2, included in the frequency-domain sample sequence obtained by the decoding part decoding the spectrum code, on a higher side than the frequency-domain sample sequence obtained by the decoding part decoding the spectrum code; and a fricative sound adjustment releasing part obtaining, if inputted information indicating whether a hissing sound or not indicates being a hissing sound, what is obtained by exchanging all or a part of a low-side frequency sample sequence existing on a lower side than a predetermined frequency in the decoded extended frequency spectrum sequence obtained by the bandwidth extending part for all or a part of a high-side frequency sample sequence existing on a higher side than the predetermined frequency in the decoded extended frequency spectrum sequence obtained by the bandwidth extending part, as a frequency spectrum sequence of a decoded sound signal, the number of all or the part of the high-side frequency sample sequence being the same as the number of all or the part of the low-side frequency sample sequence, and, otherwise, immediately obtaining the decoded extended frequency spectrum sequence obtained by the bandwidth extending part as it is, as the frequency spectrum sequence of the decoded sound signal. a decoding part decoding a spectrum code which is a spectrum code for each frame in a predetermined time section and in which bits are not assigned to a part of a high side, to obtain a frequency-domain sample sequence; a bandwidth extending part obtaining a decoded extended frequency spectrum sequence by arranging samples based on K samples, K is an integer equal to or larger than 2, included in the frequency-domain sample sequence obtained by the decoding part decoding the spectrum code, on a higher side than the frequency-domain sample sequence obtained by the decoding part decoding the spectrum code; and a fricative sound adjustment releasing part obtaining, if inputted information indicating whether a hissing sound or not indicates being a hissing sound, what is obtained by exchanging all or a part of a low-side frequency sample sequence existing on a lower side than a predetermined frequency in the decoded extended frequency spectrum sequence obtained by the bandwidth extending part for all or a part of a high-side frequency sample sequence existing on a higher side than the predetermined frequency in the decoded extended frequency spectrum sequence obtained by the bandwidth extending part, as a frequency spectrum sequence of a decoded sound signal, the number of all or the part of the high-side frequency sample sequence being the same as the number of all or the part of the low-side frequency sample sequence, and, otherwise, immediately obtaining the decoded extended frequency spectrum sequence obtained by the bandwidth extending part as it is, as the frequency spectrum sequence of the decoded sound signal.