To provide a digital signal processing apparatus and a digital signal processing method that employ a filter comprising a multistage series connection of IIR filters having a shelving characteristic (or stepping characteristic), set a plurality of set points each comprising a set of frequency and gain values, and implement an arbitrary frequency response characteristic passing the set points.

In the digital signal processing apparatus, a filter setting section includes an error calculation section for calculating an implemented frequency response characteristic H of the filter section and calculating an error E from a desired frequency response characteristic D, and sets the filter section comprising a multiple N-stage series connection of M-order IIR filters Sn having a shelving characteristic Hn indicating a cutoff frequency fc and a gain gn, by changing the cutoff frequency fc of each of the plurality of IIR filters Sn of the filter section and changing the order of each IIR filter Sn from M in response to an output from the error calculation section to reduce the error E.