When ball bearings which have flaws on the surface of the ball or races or dust in the grease are used to support the spindle of the head or capstan in a video tape recorder, such defects debase the quality of the played-back picture. A new method is proposed for the automatic detection of slight flaws or dust in ball bearings using the vibration signals. These defects, which are not detected by periodic analysis or ordinary signal processing techniques, can be easily detected at an accuracy rate of 98. 4%.