An abnormality-diagnosing device is used to diagnose if a bearing device used on the axle of a railway vehicle is normal. The abnormality-diagnosing device comprises a detection processing part, an operation processing part, a result output part and a control processing part, wherein, the detection processing part outputs the signal generated by the bearing device, which is regarded as an electric signal, the operation processing part conducts an abnormality diagnosis on the bearing device according to the output of the detection processing part, the result output part outputs the judgement result of the operation processing part, and according to the judgement result, the control processing part returns a control signal to the control system of the railway vehicle.