To identify exhalation and inhalation of a subject more accurately. A biological monitoring device (1) comprises: a monitoring unit (12) which monitors changes over time in the depth of feature points at one or a plurality of locations within a living body, on the basis of a received signal received from an ultrasonic sensor (2)； and an exhalation/inhalation identifying unit (13) which identifies exhalation or inhalation on the basis of information relating to the depth of the feature points. Contraction and expansion of the lungs, in other words exhalation and inhalation, can be identified by applying ultrasound waves from between the ribs of a subject to monitor movements of biological tissue which moves together with the lungs.
