A coding apparatus comprising: a time-frequency transform section configured to transform an input signal from a time domain to a frequency domain to obtain input transform coefficients, the input signal comprising sound-related data; a core coding section configured to encode transform coefficients in a low band lower than a reference frequency among the input transform coefficients; and an extension-band coding section configured to encode transform coefficients in an extension band by using core encoded and decoded low-band transform coefficients, the extension band being a band higher than the reference frequency, wherein the extension-band coding section comprises: a threshold calculation section configured to calculate, for each extension-band subband of extension-band subbands obtained by splitting the extension band, a threshold based on statistics on transform coefficients included in the extension-band subband; a representative transform coefficient extraction section configured to compare, for each extension-band subband of the extension-band subbands, amplitudes of the transform coefficients with the threshold to extract transform coefficients having an amplitude larger than the threshold, as representative transform coefficients; and a matching section configured to calculate, for each extension-band of the extension-band subbands, a value of correlation between the representative transform coefficients and normalized core encoded and decoded low-band transform coefficients and configured to select a subband of the low band having a largest value of correlation, wherein: the threshold calculation section is configured to update, when a number of the representative transform coefficients extracted by the representative transform coefficient extraction section is less than a predetermined number, the threshold in accordance with a shortage number of the representative transform coefficients with reference to the predetermined number; and the representative transform coefficient extraction section is configured to perform processing to extract a transform coefficient again by using the updated threshold. a time-frequency transform section configured to transform an input signal from a time domain to a frequency domain to obtain input transform coefficients, the input signal comprising sound-related data; a core coding section configured to encode transform coefficients in a low band lower than a reference frequency among the input transform coefficients; and an extension-band coding section configured to encode transform coefficients in an extension band by using core encoded and decoded low-band transform coefficients, the extension band being a band higher than the reference frequency, wherein the extension-band coding section comprises: a threshold calculation section configured to calculate, for each extension-band subband of extension-band subbands obtained by splitting the extension band, a threshold based on statistics on transform coefficients included in the extension-band subband; a representative transform coefficient extraction section configured to compare, for each extension-band subband of the extension-band subbands, amplitudes of the transform coefficients with the threshold to extract transform coefficients having an amplitude larger than the threshold, as representative transform coefficients; and a matching section configured to calculate, for each extension-band of the extension-band subbands, a value of correlation between the representative transform coefficients and normalized core encoded and decoded low-band transform coefficients and configured to select a subband of the low band having a largest value of correlation, wherein: a threshold calculation section configured to calculate, for each extension-band subband of extension-band subbands obtained by splitting the extension band, a threshold based on statistics on transform coefficients included in the extension-band subband; a representative transform coefficient extraction section configured to compare, for each extension-band subband of the extension-band subbands, amplitudes of the transform coefficients with the threshold to extract transform coefficients having an amplitude larger than the threshold, as representative transform coefficients; and a matching section configured to calculate, for each extension-band of the extension-band subbands, a value of correlation between the representative transform coefficients and normalized core encoded and decoded low-band transform coefficients and configured to select a subband of the low band having a largest value of correlation, wherein: the threshold calculation section is configured to update, when a number of the representative transform coefficients extracted by the representative transform coefficient extraction section is less than a predetermined number, the threshold in accordance with a shortage number of the representative transform coefficients with reference to the predetermined number; and the representative transform coefficient extraction section is configured to perform processing to extract a transform coefficient again by using the updated threshold.