System for diagnosis of abnormalities, diagnosis method and apparatus

There is provided an abnormality diagnostic system (10) comprising: a component (111) for obtaining a current value, which is given a value of an alternating current, which is supplied to a device under test (3) or is discharged therefrom, a frequency analysis part ( 112) which converts the current values ​​obtained in intervals into a frequency spectrum, which correlates a current intensity with a frequency, a component (113) for calculating that calculates at intervals a frequency width of the frequency spectrum at a current intensity "As" an abnormality judgment value, wherein As satisfies the following equation: As = m × at (0 frequency, which is an integer multiple of the frequency of the alternating current, and an evaluation component (114) that judges whether the frequency width is wider than under normal circumstances, and if so, judges that the Vorrich device (3) is in an abnormal state.