PURPOSE: To obtain a frequency spectrum analyzer for vehicles which can execute measurement and analysis quickly and which facilitates the operation of an inspector and has no possibility of causing a problem in terms of safety.

CONSTITUTION: A road surface state detecting means 50 for detecting a prescribed state of a road surface, a vehicle speed detecting means 51 for detecting a vehicle speed, a vehicle state detecting means 52 for detecting the state of each part of a vehicle, a filter means 53 for filtering a signal of the means 52, and a frequency spectrum analyzing means 54 for subjecting the filtered signal to Fourier transform and executing a frequency spectrum analysis, are provided. Moreover, a display and output means 55 for displaying and outputting the result of the analysis, a cut-off frequency setting means 56 for setting a cut-off frequency of the means 53 in accordance with signals of the means 50 and 51, a condition setting means 57 for setting a sampling period, a sampling time and a weight function for an input signal of the means 54 at values corresponding to the state of the road surface detected by the means 50, and a start means 58 for starting measurement automatically when the means 50 detects the prescribed state of the road surface, are provided.