A digital filter circuit comprising: an overlap addition means for generating a block including N data, N being a positive integer, from input data in a time domain by giving an overlap of M data, M being a positive integer, between the block and the previous block; an FFT processing means for transforming the generated block to a block in a frequency domain by performing FFT processing; a filter computation means for performing filter processing to the transformed block in the frequency domain and outputting a filtered block; an IFFT means for transforming the filtered block to a block in the time domain by IFFT processing; an overlap removal means for generating an output signal by removing a total of M data from both ends of the transformed block in the time domain; characterized in that: the digital filter circuit further comprises a clock generation means for setting a frequency of a filter processing clock signal based on the number M of the overlaps, wherein the filter processing clock signal drives a data output unit of the overlap addition means, the FFT means, the filter computation means, the IFFT means, and a data input unit of the overlap removal means, wherein the number N is determined based on the number M, so that the power consumption is minimized, and the frequency of the filter processing clock signal is determined based on the number N and the number M, wherein the clock generation means sets the frequency of the filter processing clock signal at N/(N-M) times a frequency of an input-output clock signal which drives a data input unit of the overlap addition means and a data output unit of the overlap removal means. an overlap addition means for generating a block including N data, N being a positive integer, from input data in a time domain by giving an overlap of M data, M being a positive integer, between the block and the previous block; an FFT processing means for transforming the generated block to a block in a frequency domain by performing FFT processing; a filter computation means for performing filter processing to the transformed block in the frequency domain and outputting a filtered block; an IFFT means for transforming the filtered block to a block in the time domain by IFFT processing; an overlap removal means for generating an output signal by removing a total of M data from both ends of the transformed block in the time domain; characterized in that: the digital filter circuit further comprises a clock generation means for setting a frequency of a filter processing clock signal based on the number M of the overlaps, wherein the filter processing clock signal drives a data output unit of the overlap addition means, the FFT means, the filter computation means, the IFFT means, and a data input unit of the overlap removal means, wherein the number N is determined based on the number M, so that the power consumption is minimized, and the frequency of the filter processing clock signal is determined based on the number N and the number M, wherein the clock generation means sets the frequency of the filter processing clock signal at N/(N-M) times a frequency of an input-output clock signal which drives a data input unit of the overlap addition means and a data output unit of the overlap removal means. the digital filter circuit further comprises a clock generation means for setting a frequency of a filter processing clock signal based on the number M of the overlaps, wherein the filter processing clock signal drives a data output unit of the overlap addition means, the FFT means, the filter computation means, the IFFT means, and a data input unit of the overlap removal means, wherein the number N is determined based on the number M, so that the power consumption is minimized, and the frequency of the filter processing clock signal is determined based on the number N and the number M, wherein the clock generation means sets the frequency of the filter processing clock signal at N/(N-M) times a frequency of an input-output clock signal which drives a data input unit of the overlap addition means and a data output unit of the overlap removal means.