An encoding apparatus comprising an encoding part encoding a frequency-domain sample sequence corresponding to a sound signal of each frame in a predetermined time section by an encoding process in which bits are preferentially assigned to a low side, to obtain a spectrum code, the encoding apparatus further comprising: a fricative sound judging part, for each frame, judging whether the sound signal is a hissing sound or not to obtain fricative sound judgment information indicating whether the sound signal is a hissing sound or not; a fricative sound adjusting part, for each frame, obtaining, if the fricative sound judging part judges that the sound signal is a hissing sound, what is obtained by exchanging all or a part of a low-side frequency spectrum sequence existing on a lower side than a predetermined frequency in a frequency spectrum sequence of the sound signal for all or a part of a high-side frequency spectrum sequence existing on a higher side than the predetermined frequency in the frequency spectrum sequence as an adjusted frequency spectrum sequence, the number of all or the part of the high-side frequency spectrum sequence being the same as the number of all or the part of the low-side frequency spectrum sequence, and, otherwise, immediately obtaining the frequency spectrum sequence corresponding to the sound signal as it is, as the adjusted frequency spectrum sequence; and a multiplexing part, for each frame, outputting a code obtained by combining a code corresponding to the fricative sound judgment information and the spectrum code, wherein the encoding part encodes the adjusted frequency spectrum sequence obtained by the fricative sound adjusting part as the frequency-domain sample sequence corresponding to the sound signal to obtain a spectrum code. a fricative sound judging part, for each frame, judging whether the sound signal is a hissing sound or not to obtain fricative sound judgment information indicating whether the sound signal is a hissing sound or not; a fricative sound adjusting part, for each frame, obtaining, if the fricative sound judging part judges that the sound signal is a hissing sound, what is obtained by exchanging all or a part of a low-side frequency spectrum sequence existing on a lower side than a predetermined frequency in a frequency spectrum sequence of the sound signal for all or a part of a high-side frequency spectrum sequence existing on a higher side than the predetermined frequency in the frequency spectrum sequence as an adjusted frequency spectrum sequence, the number of all or the part of the high-side frequency spectrum sequence being the same as the number of all or the part of the low-side frequency spectrum sequence, and, otherwise, immediately obtaining the frequency spectrum sequence corresponding to the sound signal as it is, as the adjusted frequency spectrum sequence; and a multiplexing part, for each frame, outputting a code obtained by combining a code corresponding to the fricative sound judgment information and the spectrum code, wherein the encoding part encodes the adjusted frequency spectrum sequence obtained by the fricative sound adjusting part as the frequency-domain sample sequence corresponding to the sound signal to obtain a spectrum code.