A speech coding apparatus comprising: an orthogonal transform section configured to perform modified discrete cosine transformation (MDCT) for an input signal to form spectrum data; and an algebraic vector quantization coding section configured to perform AVQ coding using the spectrum data, the AVQ coding section comprising: a global gain calculation section configured to calculate a global gain for the spectrum data, a spectrum correcting section configured to divide the spectrum data into a plurality of subbands and correct the spectrum data of each of subband, a transform section configured to transform the corrected spectrum data into a lattice vector, a multi-rate indexing section configured to calculate index information from the lattice vector, and a multiplexing section configured to multiplex the global gain with the index information to generate coded information, and output the coded information, characterized in that the spectrum correcting section is configured to correct the spectrum data of each of the subbands by calculating an average amplitude value for each subband, wherein each average amplitude value is calculated based on all samples of the spectrum data of the respective subband, and the spectrum correcting section is further configured to correct the spectrum by assigning zero to samples having an amplitude equal to or less than the average amplitude value of the respective subband. an orthogonal transform section configured to perform modified discrete cosine transformation (MDCT) for an input signal to form spectrum data; and an algebraic vector quantization coding section configured to perform AVQ coding using the spectrum data, the AVQ coding section comprising: a global gain calculation section configured to calculate a global gain for the spectrum data, a spectrum correcting section configured to divide the spectrum data into a plurality of subbands and correct the spectrum data of each of subband, a transform section configured to transform the corrected spectrum data into a lattice vector, a multi-rate indexing section configured to calculate index information from the lattice vector, and a multiplexing section configured to multiplex the global gain with the index information to generate coded information, and output the coded information, characterized in that the spectrum correcting section is configured to correct the spectrum data of each of the subbands by calculating an average amplitude value for each subband, wherein each average amplitude value is calculated based on all samples of the spectrum data of the respective subband, and the spectrum correcting section is further configured to correct the spectrum by assigning zero to samples having an amplitude equal to or less than the average amplitude value of the respective subband. a global gain calculation section configured to calculate a global gain for the spectrum data, a spectrum correcting section configured to divide the spectrum data into a plurality of subbands and correct the spectrum data of each of subband, a transform section configured to transform the corrected spectrum data into a lattice vector, a multi-rate indexing section configured to calculate index information from the lattice vector, and a multiplexing section configured to multiplex the global gain with the index information to generate coded information, and output the coded information, characterized in that the spectrum correcting section is configured to correct the spectrum data of each of the subbands by calculating an average amplitude value for each subband, wherein each average amplitude value is calculated based on all samples of the spectrum data of the respective subband, and the spectrum correcting section is further configured to correct the spectrum by assigning zero to samples having an amplitude equal to or less than the average amplitude value of the respective subband.