PURPOSE: To obtain a circuit simulation device capable of outputting a simulation result corresponding to practical circuit characteristics by executing transient analysis in each frequency of an input signal supplied to a circuit to be simulated and finding out the mean value of the ratios of the amplitude values of the input signal to that of an output signal corresponding to the input signal in each frequency.

CONSTITUTION: A transient analysis executing part 13 executes the transient analysis of a circuit or an element to be simulated in each frequency of an input signal and a mean value calculating part 14 calculates the ratio of the amplitude value of an input signal to that of an output signal in each frequency of the input signal and finds out the mean value of the ratio data. A mean value output part 15 outputs the mean value of the ratios of the amplitude values of the input signal to that of the output signal calculated by the calculating part 14 as a simulation result, so that an analytical result corresponding to practical circuit characteristics can be obtained.