third aspect of the invention is characterized in that the equivalent circuit creating step comprises a functional block power equivalent circuit creating step of creating a degenerate impedance circuit of each functional block in a semiconductor integrated circuit from the impedance information and an inter-block power equivalent circuit creating step of creating a circuit for analyzing the inter-block power wiring in the semiconductor integrated circuit from the impedance information and that the analysis step uses as the equivalent circuit at least one of the degenerate impedance circuit and the circuit for analyzing the inter-block power wiring. The fourth aspect of the invention is characterized in that the equivalent circuit creating step comprises a functional block power equivalent circuit creating step of creating a degenerate impedance circuit of each functional block in a semiconductor integrated circuit from the impedance information, an inter-block power equivalent circuit creating step of creating a circuit for analyzing the inter-block power wiring in the semiconductor integrated circuit from the impedance information and an 