A respiratory rate measuring method and apparatus including a wearable device that utilizes a heartbeat signal to detect the respiratory rate without motion detection of a patients body. The method includes extracting a heartbeat signal, extracting an amplitude modulation (AM) signal and a frequency modulation (FM) signal through AM and FM with respect to the extracted heartbeat signal, respectively, performing normalization on the AM signal and the FM signal. The normalized AM signal and the normalized FM signal are combined into a single combined normalized signal, and a respiratory rate is calculated by extracting a respiratory frequency band from the combined normalized signal.
