PURPOSE: To obtain a method and an apparatus wherein the influence of a noise signal on a device under test is evaluated by a method wherein the change with the time of a frequency response function and the amplitude of the frequency response function are measured.

CONSTITUTION: A method and an apparatus wherein the influence of a noise signal on a device under test is evaluated is provided with the following: a buffer device 32 which stores the time waveform of a noise output signal from the device, under test, which has been influenced by the noise signal caused and generated by the operation itself of the device under test due to an input signal; and a buffer device 31 which stores the time waveform 41 of the input signal. They are provided with a device which finds a frequency response function by reading out the following at each set time interval: the time waveform 42 of the noise output signal stored in the buffer device 32; and the time waveform 41 of the input signal stored in the buffer device 31. They provide a device 90 which displays and observes the change with the time of the frequency response function regarding a set frequency.