The invention discloses an abnormal vibration detection device for a numerically-controlled machine tool. The abnormal vibration detection device comprises an input circuit of three paths of vibration signals and a controller used for signal processing. The invention also discloses a detection method of the abnormal vibration detection device for the numerically-controlled machine tool. According to the detection method, filtering of different frequencies is carried out on vibration signals; and decomposition and comparison are performed on filtered signals, so that the independent vibration information of each vibration source can be obtained. With the abnormal vibration detection device and the detection method of the invention adopted, defects in the prior art can be eliminated, and the accuracy of judgment on the operation state of the machine tool through vibration can be improved.