A digital filter has a plurality of filters, wherein each filter performs coefficient multiplication and delay processing for an input signal and an output signal, obtains the output signal from the input signal, and includes a plurality of coefficient multipliers for multiplying a signal by a predetermined coefficient. The digital filter also includes a plurality of delay circuits for delaying a signal, and an adder for adding a plurality of signals. A first RAM stores a plurality of sets of coefficient data for a plurality of coefficient multipliers of the first filter and stores delay data for the delay circuit of the second filter. A second RAM stores a plurality of sets of coefficient data for a plurality of coefficient multipliers of the second filter and stores delay data for the delay circuit of the first filter.