An encoding device, comprising: a normalization means for extracting an envelope from a spectrum of an audio signal and for normalizing the spectrum using the envelope; an envelope emphasis means for emphasizing the envelope; a noise shaping means for dividing the envelope (D; D[k]) emphasized by the envelope emphasis means by a value larger than 1, and for subtracting noise shaping (G[k]) specified by predetermined information from the envelope (D[k]/2) emphasized by the envelope emphasis means and divided by the value larger than 1, resulting in quantization information (WL; WL[k]); a quantization means for setting the quantization information (WL; WL[k]) as a quantization bit count and for quantizing the spectrum normalized by the normalization means, based on the quantization bit count and for feeding a bit count N in the quantized spectrum back to the noise shaping means; and a multiplexing means for multiplexing the predetermined information, the spectrum quantized by the quantization means and the envelope, wherein: the noise shaping means determines whether the bit count in a bit stream (BS') falls within a desired range based on the bit count N, if it is determined that the bit count in the bit stream (BS') does not fall within the desired range, the noise shaping means newly decides predetermined information so that the bit count in the bit stream (BS') falls within the desired range and new quantization information WL is supplied to the quantization means, if it is determined that the bit count in the bit stream (BS') falls within the desired range, the noise shaping means instructs the quantization means to produce an output and supplies current predetermined information to the multiplexing means, and the predetermined information is information indicative of a lowest value and a highest value of the noise shaping. a normalization means for extracting an envelope from a spectrum of an audio signal and for normalizing the spectrum using the envelope; an envelope emphasis means for emphasizing the envelope; a noise shaping means for dividing the envelope (D; D[k]) emphasized by the envelope emphasis means by a value larger than 1, and for subtracting noise shaping (G[k]) specified by predetermined information from the envelope (D[k]/2) emphasized by the envelope emphasis means and divided by the value larger than 1, resulting in quantization information (WL; WL[k]); a quantization means for setting the quantization information (WL; WL[k]) as a quantization bit count and for quantizing the spectrum normalized by the normalization means, based on the quantization bit count and for feeding a bit count N in the quantized spectrum back to the noise shaping means; and a multiplexing means for multiplexing the predetermined information, the spectrum quantized by the quantization means and the envelope, wherein: the noise shaping means determines whether the bit count in a bit stream (BS') falls within a desired range based on the bit count N, if it is determined that the bit count in the bit stream (BS') does not fall within the desired range, the noise shaping means newly decides predetermined information so that the bit count in the bit stream (BS') falls within the desired range and new quantization information WL is supplied to the quantization means, if it is determined that the bit count in the bit stream (BS') falls within the desired range, the noise shaping means instructs the quantization means to produce an output and supplies current predetermined information to the multiplexing means, and the predetermined information is information indicative of a lowest value and a highest value of the noise shaping. the noise shaping means determines whether the bit count in a bit stream (BS') falls within a desired range based on the bit count N, if it is determined that the bit count in the bit stream (BS') does not fall within the desired range, the noise shaping means newly decides predetermined information so that the bit count in the bit stream (BS') falls within the desired range and new quantization information WL is supplied to the quantization means, if it is determined that the bit count in the bit stream (BS') falls within the desired range, the noise shaping means instructs the quantization means to produce an output and supplies current predetermined information to the multiplexing means, and the predetermined information is information indicative of a lowest value and a highest value of the noise shaping.