PURPOSE: To prevent the occurrence of an accident by invariably monitoring the abnormality of the rolling bearing of the rotary shaft of a machine tool and various industrial machines, automatically predicting and judging the abnormality such as vibration with a computer, and automatically operating the deceleration or stop of the machine.

CONSTITUTION: An acceleration sensor 3 is installed in a bearing box 1 supporting a spindle. A charge amplifier 4, a band-pass filter 5 and an A/D converter 6 converting the signal from the acceleration sensor 3 into voltage are connected in sequence with analog signal lines 9. A computer 7 is connected to the A/D converter 6 via a digital signal line 10, the abnormality prediction risk signal of a bearing is sent to a controller 8 based on the digital data of the vibration of the rolling bearing, and a motor 2 is decelerated or stopped.