An abnormality detection device of a machine tool includes a plurality of vibration sensors mounted on a body of the machine tool at a plurality of positions; and a determination portion that determines an operation condition of the machine tool based on vibration information detected by the vibration sensors. The abnormality detection device detects abnormality of the machine tool according to determination information of the determination portion. The determination portion specifies a predetermined item whose machining accuracy lowers based on the mounted position of the vibration sensor that has detected abnormal vibration.