PURPOSE: To realize the digital filter able to attain high speed response.

CONSTITUTION: A digital data given in terms of a serial signal is fetched by an N-bit shift register 1. A parallel bit data outputted from the N-bit shift register 1 is given to an address input terminal of a memory 10. A coefficient h(n) specifying an impulse response characteristic is multiplied with each bit data of an address signal in each address of the memory 10 depending on the N-bit data and the total sum of the result of multiplication is stored. The N-bit data is given to an address input terminal of the memory 10 to read a digital value corresponding to an output voltage of the digital filter from the memory 10. The digital value is D/A-converted to obtain an output voltage of the digital filter.