Abstract: A method of detecting abnormalities includes: calculating a reference failure rate using failure data at a plurality of points in time included in a particular period; calculating a detection failure rate and weighting, corresponding to failure data at a detection time point after the particular period, using the reference failure rate; calculating an abnormality index based on multiplying the detection failure rate by the weighting; comparing the abnormality index with an index corresponding to a control limit for stably controlling a failure rate; and detecting whether the failure data at the detection time point is abnormal, based on a result of the comparison of the abnormality index with the index corresponding to the control limit.