A multimode speech coding apparatus, comprising: first coding means (102, 103) adapted for coding at least one type of parameter indicative of vocal tract information contained in a speech signal; second coding means (109, 110, 111) adapted for being capable of coding said at least one type of parameter indicative of excitation signal information contained in a speech signal with a plurality of modes; mode switching means (105, 621) adapted for switching a coding mode of said second coding means based on a mode determination indicating a speech region or a non-speech region; and synthesis means adapted for synthesizing an input speech signal using a plurality of types of parameter information coded in said first coding means and said second coding means; characterized by further comprising an extractor of parameters adapted for extracting characteristics of parameters indicative of vocal tract information, and a speech region detector adapted for detecting a speech region or a non-speech region, wherein the extractor comprises: means (604, 605, 606, 607) adapted for calculating an evolution of a quantized LSP (Line Spectrum Pair) parameter between frames; means (608, 609, 610, 611) adapted for calculating an average quantized LSP parameter in a frame in which the quantized LSP parameter is stationary; and means (612, 613) adapted for calculating a difference between said average quantized LSP parameter and a current quantized LSP parameter, and wherein the speech region detector is adapted for detecting whether or not an input signal is a speech region or a non-speech region, and judging the input signal is a speech region, when the calculated evolution of a quantized LSP parameter between frames (first dynamic parameter: Para 1) is greater than a first predetermined threshold or the calculated difference between the average quantized LSP parameter and the current quantized LSP parameter (second dynamic parameter: Para 2) is greater than a second predetermined threshold. first coding means (102, 103) adapted for coding at least one type of parameter indicative of vocal tract information contained in a speech signal; second coding means (109, 110, 111) adapted for being capable of coding said at least one type of parameter indicative of excitation signal information contained in a speech signal with a plurality of modes; mode switching means (105, 621) adapted for switching a coding mode of said second coding means based on a mode determination indicating a speech region or a non-speech region; and synthesis means adapted for synthesizing an input speech signal using a plurality of types of parameter information coded in said first coding means and said second coding means; characterized by further comprising an extractor of parameters adapted for extracting characteristics of parameters indicative of vocal tract information, and a speech region detector adapted for detecting a speech region or a non-speech region, wherein the extractor comprises: means (604, 605, 606, 607) adapted for calculating an evolution of a quantized LSP (Line Spectrum Pair) parameter between frames; means (608, 609, 610, 611) adapted for calculating an average quantized LSP parameter in a frame in which the quantized LSP parameter is stationary; and means (612, 613) adapted for calculating a difference between said average quantized LSP parameter and a current quantized LSP parameter, and wherein the speech region detector is adapted for detecting whether or not an input signal is a speech region or a non-speech region, and judging the input signal is a speech region, when the calculated evolution of a quantized LSP parameter between frames (first dynamic parameter: Para 1) is greater than a first predetermined threshold or the calculated difference between the average quantized LSP parameter and the current quantized LSP parameter (second dynamic parameter: Para 2) is greater than a second predetermined threshold. means (604, 605, 606, 607) adapted for calculating an evolution of a quantized LSP (Line Spectrum Pair) parameter between frames; means (608, 609, 610, 611) adapted for calculating an average quantized LSP parameter in a frame in which the quantized LSP parameter is stationary; and means (612, 613) adapted for calculating a difference between said average quantized LSP parameter and a current quantized LSP parameter, and wherein the speech region detector is adapted for detecting whether or not an input signal is a speech region or a non-speech region, and judging the input signal is a speech region, when the calculated evolution of a quantized LSP parameter between frames (first dynamic parameter: Para 1) is greater than a first predetermined threshold or the calculated difference between the average quantized LSP parameter and the current quantized LSP parameter (second dynamic parameter: Para 2) is greater than a second predetermined threshold.