Noise current flowing to the outside of an IC (1) with respect to the capacitance value and arrangement location of a bypass capacitor (4) is calculated on the basis of the impedance of current paths (P1, P2) passing via a bypass capacitor (4) at the outside of the IC (1) and the impedance of the inside of IC (1) when viewed from power supply terminals (2, 3) of the IC (1). The capacitance value and arrangement location of the bypass capacitor (4) are determined on the basis of the calculation result.