There is provided a biological information monitoring system for monitoring biological information of a subject on a bed, the system comprising: detectors which detect load of the subject； a center of gravity position calculating unit which acquires temporal variation of a center of gravity position of the subject based on the detected load； a body motion information determining unit which acquires information on body motion of the subject based on the acquired temporal variation； and a respiratory rate calculating unit which calculates a respiratory rate of the subject based on the acquired temporal variation and the information on the body motion of the subject. The body motion information includes information on large and small body motions of the subject, and the body motion information determining unit includes first and second body motion information determining units which determine the information on the large and small body motions of the subject, respectively.
