There is provided a power supply voltage fluctuation analyzing method which performs power supply voltage fluctuation analysis for a semiconductor product, and the method comprises a step of determining a power consumption distribution in each function cell of the semiconductor product by using a power supply portion position and a ratio of each portion based on stored information of an input library which stores therein the power supply portion position and ratio information for each function cell of the semiconductor product, and allocating a power consumption to each function cell.
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