A speech/audio coding apparatus comprising: a receiver that receives a time-domain speech/audio input signal; a memory; and a processor that transforms the speech/audio input signal into a frequency domain; splits a frequency spectrum of the speech/audio signal to obtain a plurality of subbands; estimates an energy envelope which represents an energy level for each of the plurality of subbands; quantizes the energy envelope; determines a plurality of groups from the quantized energy envelope, each of the plurality of groups being composed of a plurality of subbands; allocates bits to the determined plurality of groups on a group-by-group basis; allocates the bits allocated to each of the plurality of groups to the plurality of subbands included in each of the groups on a subband-by-subband basis; and encodes the frequency spectrum using the bits allocated to the subbands, wherein, when determining the plurality of groups, the processor identifies one or more dominant groups which are composed of a dominant frequency subband in which an energy envelope of the frequency spectrum has a local maximum value and mutually adjacent subbands on both sides of the dominant frequency subband, the mutually adjacent subbands each forming a descending slope of an energy envelope, and identifies one or more non-dominant groups which are composed of mutually adjacent subbands other than those included in the one or more dominant groups. a receiver that receives a time-domain speech/audio input signal; a memory; and a processor that transforms the speech/audio input signal into a frequency domain; splits a frequency spectrum of the speech/audio signal to obtain a plurality of subbands; estimates an energy envelope which represents an energy level for each of the plurality of subbands; quantizes the energy envelope; determines a plurality of groups from the quantized energy envelope, each of the plurality of groups being composed of a plurality of subbands; allocates bits to the determined plurality of groups on a group-by-group basis; allocates the bits allocated to each of the plurality of groups to the plurality of subbands included in each of the groups on a subband-by-subband basis; and encodes the frequency spectrum using the bits allocated to the subbands, wherein, when determining the plurality of groups, the processor identifies one or more dominant groups which are composed of a dominant frequency subband in which an energy envelope of the frequency spectrum has a local maximum value and mutually adjacent subbands on both sides of the dominant frequency subband, the mutually adjacent subbands each forming a descending slope of an energy envelope, and identifies one or more non-dominant groups which are composed of mutually adjacent subbands other than those included in the one or more dominant groups. transforms the speech/audio input signal into a frequency domain; splits a frequency spectrum of the speech/audio signal to obtain a plurality of subbands; estimates an energy envelope which represents an energy level for each of the plurality of subbands; quantizes the energy envelope; determines a plurality of groups from the quantized energy envelope, each of the plurality of groups being composed of a plurality of subbands; allocates bits to the determined plurality of groups on a group-by-group basis; allocates the bits allocated to each of the plurality of groups to the plurality of subbands included in each of the groups on a subband-by-subband basis; and encodes the frequency spectrum using the bits allocated to the subbands, wherein, when determining the plurality of groups, the processor identifies one or more dominant groups which are composed of a dominant frequency subband in which an energy envelope of the frequency spectrum has a local maximum value and mutually adjacent subbands on both sides of the dominant frequency subband, the mutually adjacent subbands each forming a descending slope of an energy envelope, and identifies one or more non-dominant groups which are composed of mutually adjacent subbands other than those included in the one or more dominant groups. identifies one or more dominant groups which are composed of a dominant frequency subband in which an energy envelope of the frequency spectrum has a local maximum value and mutually adjacent subbands on both sides of the dominant frequency subband, the mutually adjacent subbands each forming a descending slope of an energy envelope, and identifies one or more non-dominant groups which are composed of mutually adjacent subbands other than those included in the one or more dominant groups.