PURPOSE: To correct an error of a system of the digital filter circuit having a pre-stage and a post-stage circuit such as a low pass filter at an input/output section and having an A/D converter or a D/A converter implementing the conversion between an analog signal and a digital signal and to obtain a required characteristic.

CONSTITUTION: The filter circuit is provided with switches 11-13, 15,16 able to be controlled by a digital filter arithmetic section 4 so as to fetch an input or an output signal of a front end circuit 10 and a back end circuit 14 as data and they are operated to fetch error data of the pre-stage circuit 10 and the post-stage circuit 14 and to implement arithmetic processing thereby eliminating an error as the system and obtaining a required characteristic for the digital filter.