1. An acoustic signal coding apparatus comprising: a time-to-frequency converter that converts an input signal to a spectrum in a frequency domain; a divider that divides the spectrum in the frequency domain into subbands; a subband classifier that classifies the subbands into a plurality of perceptually important first-category subbands and the other subbands referred to as second-category subbands according to at least one of measures in terms of energy and peak property; an SBP-AVQ vector generator that generates an SBP-AVQ vector by collecting a maximum peak from each first-category subband, outputs the generated SBP-AVQ vector, and outputs peak position information indicating the positions of the maximum peaks; a bit distributor that distributes bits for AVQ coding to the SBP-AVQ vector and the second-category subband vector; an AVQ coder that performs AVQ coding using the bits on the SBP-AVQ vector and the second-category subband; and a multiplexer that outputs a multiplexed signal in which the AVQ-coded signal and the peak position information are multiplexed.