A finite impulse response (FIR) filter circuit design method using approximate computing, the FIR filter circuit design method including: replacing adders of the FIR filter with approximate adders; and performing a synthesis work according to a set approximate synthesis flow when the replacing of the adders of the FIR filter are replaced with the approximate adders is performed, wherein, in the approximate synthesis flow, a numeric column of each of the approximate adders is divided into an accurate part and an inaccurate part, and a numeric column of the inaccurate part is approximated. In the FIR filter, conventional adders/subtractors are replaced with addition/subtraction having an automated synthesis flow so that energy consumption can be reduced.