Provided is an atrial fibrillation detection system which can reduce the burden on a test subject, with which it is possible to detect even paroxysmal atrial fibrillation, and which can be used in the home, contributing to early detection of atrial fibrillation. This atrial fibrillation detection system detects the presence of atrial fibrillation in a subject, and is provided with a heartbeat period measurement means that measures heartbeat periods of the heart； a normalized heartbeat period computation means that computes normalized heartbeat periods DR(N) from heartbeat periods of the heart measured by the heartbeat period measurement means； an abnormal normalized heartbeat period cumulation means that, from among a prescribed number of successive normalized heartbeat periods DR(N), adds up the count of abnormal normalized heartbeat periods that have an absolute value exceeding a normal heartbeat period value； and a comparison/determination means that compares the cumulative count of the abnormal normalized heartbeat periods and a normal cumulative count threshold value, and in the event that the cumulative count of the abnormal normalized heartbeat periods exceeds the normal cumulative count threshold value, determines that atrial fibrillation has occurred.
