A portable electrical apparatus includes a sensor, a micro-controller, and a wireless positioning module. The sensor is configured for sensing a movement of the portable electrical apparatus to generate a sensing signal. The micro-controller is configured for receiving the sensing signal and comparing a threshold value with a sensing value corresponding to the sensing signal. The wireless positioning module is configured for positioning the portable electrical apparatus to generate a plurality of position data corresponding to a location of the portable electrical apparatus. When the sensing value is greater than the threshold value, the micro-controller loads the position data generated within a predetermined period, which is right after the sensing value being greater than the threshold value, compares the loaded position data with each other, and an alarm signal is sent out according to a comparison result.