A wearable device is provided. The wearable device includes a photon sensor, a processor, and an output unit. The photon sensor senses light reflected from a specific region and transforms the sensed light to a plurality of electric-signal components. The processor receives the electric-signal components sensed within a period to form a dimensional sensing signal. The processor extracts a feature of a waveform of the dimensional sensing signal and determines whether a predetermined heart condition of the object is present according to the feature of the waveform of the dimensional sensing signal to generate a determination signal. The output unit is coupled to the processor. The output unit receives the determination signal and generates an alarm signal according to the determination signal.
