To reduce labor hours for setting a frequency band of higher harmonics, in a spurious signal measurement using a spectrum analyzer, thereby improving the accuracy of the measurement.

In the measurement using the spectrum analyzer 1, the center frequency (transmission frequency) of a signal transmitted from a wireless device 1 and its frequency bandwidth are measured, and the center frequency and the frequency band of the higher harmonics are calculated, in the region of the object frequency to be measured. Then, the region of the object frequency to be measured is divided into measurement frequency ranges, bounded by the higher harmonics and their fundamental harmonic, and spurious signal measurements are carried out respectively. In the measurements, an RBW (resolution of bandwidth) value to be used is set with respect to each measurement frequency range, or is set, based on the frequency bandwidth of the measurement frequency range which has the narrowest bandwidth. Detected spurious data of respective measurement frequencies are supplied to a PC 3, analyzed and output therefrom.