PROBLEM TO BE SOLVED: To provide a simple device and a method for testing the strength for withstanding an electromagnetic interference wave capable of greatly shortening the time spent for immunity test.SOLUTION: The present invention comprises: a receiving antenna 101 for receiving an electromagnetic interference wave radiated from an electronic apparatus; a receiving unit 102 for receiving from the receiving antenna; a signal processing unit 103 for converting the time waveform of the received electromagnetic interference wave into a frequency spectrum and calculating an electric field intensity level; a storage unit 104 for storing the electromagnetic interference wave converted into the frequency spectrum; an arithmetic unit 105 for calculating, when electromagnetic interference waves each converted into a plurality of frequency spectra are accumulated in the storage unit, a difference between the electromagnetic interference waves; a comparison unit 106 for comparing the electric field intensity level w
