To provide a method for designing a proper random vibration test specification by finding a shortening rate of a test time by using a peculiar accumulated fatigue calculation method, while applying correspondingly a linear damage rule.

This test specification design method for random vibration has a step of dividing a PSD data of the random vibration into a prescribed number of divisions, a step of counting random vibration waveforms in each division, a step of obtaining a distribution histogram A by performing multiplication by an each-divisional constitution ratio of the distribution histogram in each division, to be added respectively, a step of obtaining a distribution histogram B by deleting a data existing outside a range of a prescribed value, from the histogram A, a step of normalizing the distribution histogram A with an equivalent acceleration G0, to find a corresponding equivalent frequency NA, a step of normalizing the distribution histogram B with the same equivalent acceleration G0 as that in case of the distribution histogram A, to find a corresponding equivalent frequency NB, and a step of finding a ratio of the equivalent frequency NA to the equivalent frequency NB.