1. A vector quantization apparatus comprising: a first selecting section that selects a classification code vector indicating a type of a feature correlated with a quantization target vector, from a plurality of classification code vectors; a second selecting section that selects a first codebook associated with the selected classification code vector from a plurality of first codebooks; a first quantization section that quantizes the quantization target vector using a plurality of first code vectors forming the selected first codebook, to produce a first code; a third selecting section that selects a first additive factor vector associated with the selected classification code vector from a plurality of additive factor vectors; and a second quantization section that quantizes a vector related to a first residual vector between the first code vector indicated by the first code and the quantization target vector, using a plurality of second code vectors and the selected first additive factor vector, to produce a second code.