A noncontact vibration sensor includes a wireless transceiver, a filter and an amplitude demodulation unit. The wireless transceiver transmits a wireless signal to an object and receives a reflected signal from the object. Wherein the wireless transceiver is injection-locked by the reflected signal and generates a self-injection-locked signal. The filter electrically connects to the wireless transceiver for receiving the self-injection-locked signal, and the filter transforms the self-injection-locked signal from the frequency modulation to the amplitude modulation and outputting an amplitude modulated signal. The amplitude demodulation unit electrically connects to the filter for receiving the amplitude modulated signal, and the amplitude demodulation unit amplitude demodulates the amplitude modulated signal to output a demodulated signal.一種非接觸式振動感測器包含一無線收發裝置、一濾波器及一振幅解調單元，該無線收發裝置用以發出一發射訊號至一物體，並接收由該物體反射之一反射訊號，且該無線收發裝置被該反射訊號注入鎖定而產生一自我注入鎖定訊號，該濾波器電性連接該無線收發裝置以接收該自我注入鎖定訊號，且該濾波器將該自我注入鎖定訊號由頻率調制轉換為振幅調制而輸出一振幅調制訊號，該振幅解調單元電性連接該濾波器以接收該振幅調制訊號，且該振幅解調單元對該振幅調制訊號進行振幅解調而輸出一解調訊號。
