Abstract: A tab coefficient updating device of an FIRADF capable of greatly reducing the amount of hardware therefor and integrating its tab coefficient updating value operating circuit using a simple circuit design. The tab coefficient updating device includes a finite impulse-responding adaptive digital filter unit for filtering an input signal using a tab coefficient updated for a predetermined one of all tabs by a tab coefficient signal and a tab address signal, and a tab address generating unit for generating the tab address signal associated with the predetermined tab of the finite impulse-responding adaptive digital filter unit and applying the generated tab address signal to a tab coefficient updating value operating unit as well as the finite impulse-responding adaptive digital filter unit.