1. A heart-sound analyzing apparatus, comprising a heart-sound microphone which is adapted to be worn on a living subject to iteratively detect a second heart sound II of the subject; a respiration-synchronous-signal detecting device which iteratively detects a respiration-synchronous signal of the subject; an inspiration-expiration judging means for judging, based on each of the respiration-synchronous signals iteratively detected by the respiration-synchronous-signal detecting device, whether the subject is in an inspiring state or in an expiring state; and an aortic-valve-closing-timing determining means for iteratively determining a timing when an aortic valve of a heart of the subject closes, based on each of a plurality of second heart sounds II which are iteratively detected by the heart-sound microphone in a plurality of time intervals, respectively, in each of which the subject is judged as being in the inspiring state by the inspiration-expiration judging means.