A power-supply design system for designing a power supply of electronic equipment apparatuses. The system includes an input device for inputting circuit information about the power supply of the electronic equipment apparatus; a current deviation computation unit that computes an electric current deviation which indicates electric current variation of the electronic equipment apparatus, based on the circuit information input using the input device, and dispersion information that indicates a dispersion of an electric current variation, which corresponds to the circuit information; a target impedance computation unit that computes a target impedance as a target for the power supply indicated by the circuit information, based on the electric current deviation computed by the current deviation computation unit and a permissible range of a voltage variation, where the permissible range is indicated by the circuit information; and an output device that outputs the target impedance computed by the target impedance computation unit.