To provide a noise shaper of a small circuit scale and a high definition and a digital/digital converter using this.

The output value of a quantizer 12 is bit-inverted by an inverter 18. This is shifted by a shift register 21 according to the digit of a bit, which becomes 1 of the 2's complement of a feedback coefficient K3. One is added to a lowest-order bit by an adder 4 and added to a PCM signal X which is an input signal. Thus, it is realized to add the output value of the quantizer 12 which is substantially multiplied by the feedback coefficient K3 and an input signal, thereby multiplying processing is simplified to advance operation acceleration and the reduction of a circuit scale. Thus, it is possible to realize high qualification of the noise shaper by making the high frequency and the high order of a sampling frequency.