An apparatus for detecting abnormal vibrations of a rotor includes a vibration information receiver configured to receive at least one type of information among vibration information regarding one or more dimensions distinguishing locations and directions of the rotor and rotor rotation information including a number of rotations of the rotor, a multivariate management index calculator configured to calculate multivariate management indexes from the vibration information regarding the one or more dimensions, and an operation index extractor configured to determine an abnormality in vibration characteristics of the rotor when a Hotelling's T-squared value is greater than an upper control limit and extracts an operation index causing the abnormality in the vibration characteristics of the rotor from one or more operation indexes. An abnormal vibration in a rotor is detected based on four-dimensional (4D) vibration information distinguishing locations and directions of the rotor.