A data generation unit generates second abnormal sound data indicating a change in loudness of a sound each time a rotation state changes by a certain amount, based on first abnormal sound data that is data of an abnormal sound generated due to a rotary motion of a rotation device mounted on an object, and rotation data that is data relating to the rotary motion of the rotation device. The second abnormal sound data is input to a sound source estimation unit, and a certainty factor of being a sound source of the abnormal sound indicated by the second abnormal sound data is output to each of a plurality of parts mounted on a vehicle.