An abnormality detecting apparatus (10) for a rotating machine includes: a calculating part (15) which calculates a phase difference between signals respectively output from two sensors of one or more sets, the one or more sets being predetermined combinations of two sensors among the plurality of sensors, the plurality of sensors each of which detects an elastic wave generating in the rotating machine (1) having a rotor during rotation of the rotor, the sensors being arranged at predetermined different locations of the rotating machine (1); a storing part (16) which stores in advance information concerning a relationship between a phase difference and a contact position when a contact occurs during the rotation of the rotor, regarding the one or more sets; and a specifying part (17) which specifies a contact position by using a phase difference calculated by the calculating part (15) and the information stored in the storing part (16).
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