To provide an intermodulation distortion measuring method capable of easily measuring distortion of a circuit board without deteriorating characteristics of the circuit board of a measuring target.

An intermodulation distortion measuring holder 3 is formed by forming holder side conductor strip patterns 32 and holder side ground conductor patterns 33 on one surface of a holder side substrate 31, a coaxial cables 41 are connected to the intermodulation distortion measuring holder 3, the intermodulation distortion measuring holder 3 is overlapped on a circuit board 2, the holder side conductor strip patterns 32 are electrically connected to conductor strip patterns 22 of the circuit board 2 and the holder side ground conductor patterns 33 are electrically connected to ground conductor patterns 23 of the circuit board 2, an input signal A for intermodulation distortion measurement is inputted from the coaxial cables 41 to the circuit board 2 through the intermodulation distortion measuring holder 3, an output signal B outputted from the circuit board 2 to the coaxial cables 41 is measured, and intermodulation distortion of the circuit board 2 is measured on the basis of the output signal B.