PURPOSE: To decrease quantization width without greatly spoiling encoding efficiency and obtain a signal of high quality when adjacent signals are quantized at the time of quantization combined with zero-run length encoding.

CONSTITUTION: A quantizer 103 when receiving an input signal (a), a quantization control signal (b) specifying the quantization width, and a quantization variation signal (c) indicating information on quantization outputs the output signal (d) generated by quantizing the input signal and a quantization decision signal (e) indicating information on the quantization. A delay unit 104 delays the quantization variation signal and outputs it to the quantizer 103.