This instant disclosure provides a heart rate detecting module which includes an image sensor and a processor. The image sensor generates a plurality of image frames according to a light from a subject. The processor outputs a heart rate value based on a light intensity variance of the plurality of image frames. This instant disclosure further provides a heart rate detecting method which includes the following steps. A plurality of image frames are generated according to a light from a subject by an image sensor, and a heart rate value is outputted based on a light intensity variance of the plurality of image frames by a processor.
