A heartbeat-signal detecting device, which is for detecting a heartbeat signal of a living body, includes: (a) a gas-flow sensor configured to detect a flow rate of exhalation and inhalation passing through a trachea of the living body； (b) a gas-flow calculation controlling portion configured to output a respiration signal that reflects a respiratory motion of the living body, based on a signal outputted from the gas-flow sensor； (c) a waveform analysis controlling portion configured to extract, from the respiration signal, frequency components which are in synchronization with a pulse of a heart of the living body superimposed on the respiration signal, and to output a heartbeat signal representing a heartbeat waveform of the living body； and (d) a heartbeat-signal evaluation controlling portion is configured to evaluate a functional abnormality or an anatomic abnormality of the heart, based on the heartbeat signal analyzed by the waveform analysis controlling portion.
