To provide a rotary machine unit abnormality detecting system where various kinds of phenomena caused during the work of a rotary machine are previously grasped, the damage of a rotor, etc., is prevented and a producing device is efficiently maintained and managed while keeping the work of the device.

Plural system rotary machine units 1 are provided, at least one system rotary unit 1 is made to work, remaining system rotary machine units 1 are provided as the spare one and a change-over means 3 is provided, which is provided at least more than one means for detecting the respective sensor outputs of vibration sensors 9, temp. sensors 8 and pressure sensors 10 arranged in the rotary machine units 1 during working or motor driving power and also which changes over the rotary machine unit system during working into the preliminary rotary machine unit system when one of respective detecting values becomes out of a prescribed range.