PURPOSE: To make the time of occurrence of abnormality exact and to improve design precision and the reliability of a product by conducting a vibration test by giving a minute random wave to a vibration signal, and by detecting only a frequency signal of a resonant point of a test specimen.

CONSTITUTION: A test specimen 1 is vibrated 3 by a wave obtained by synthesizing 10 a sine wave from a transmitter 4 and a minute random wave from a random wave generator 9. A vibration speed is detected by a vibration sensor 6, amplified 7 and subjected to a frequency analysis and thereby a resonant point of the specimen can be detected. The frequency of this resonant point also changes due to a change in a spring constant which is caused by the occurrence of abnormality, such as the occurrence of a crack or loosening of a bolt, in the test specimen 1 in the course of a vibration test. A number of resonant points of this test specimen 1 are converted into electric signals through a plurality of band-pass filters 24 passing only the respective frequencies thereof and through F-V converters 25 converting signals of the frequencies into corresponding direct-current signals, and are stored. When a value set beforehand is reached, the test is discontinued automatically and the abnormality can be detected from a record.