A quantization device and quantization method are provided that reduce coding distortion with a small degree of calculation and achieve adequate coding performance thereby. A multistage vector quantization unit treats a number of candidates N that are designated prior to operation in the first-stage vector quantization unit, decrements the number of candidates by one beginning with the second-stage vector quantization unit and continuing with each stage thereafter. If the number of candidates is three or less, the multistage vector quantization unit assesses the quantization distortion at each stage, treating the number of candidates at the following stage as a predetermined value P if the quantization distortion is greater than a prescribed threshold, and treating the number of candidates at the following stage as a value Q that is less than the predetermined value P if the quantization distortion is less than or equal to the predetermined threshold.