To miniaturize a digital filter.

A digital band limit filter circuit 13 comprises a reference clock generation part 17, a shift register 18, a filter characteristic selection part 19, a storage part 20 and a serial signal conversion part 21. In order to enable the part 19 to select four types of filter functions, the output data equivalent to the 1st-4th filter functions are previously stored in the part 20. Then n-bit input data and 2-bit code data sent from the part 19 are supplied to the part 20 as the address data for obtaining the output data of the relevant filter function.