1. A vector quantization apparatus for a parameter vector obtained by an LPC analysis of an input speech signal, the apparatus comprising: an LPC analyzing section that analyzes the input speech signal to obtain linear predictive coefficients; a conversion section that converts the linear predictive coefficients to the parameter vector; a target vector extracting section that extracts a target vector from the parameter vector; a first quantizing section that performs a first stage of the coding of the target vector using a first code vector stored in a first codebook; an amplifier storing section that stores a scalar; and a second quantizing section that determines a third code vector by multiplying a second code vector stored in a second codebook and the scalar together, performs distance calculation using the target vector, the first code vector and the third code vector and performs a second stage of the coding of the target vector using a result of the distance calculation, to generate the quantized parameter vector, wherein the amplifier storing section outputs the scalar predetermined to be used, when the first code vector is used in the second quantizing section.