Provided is a motion detection system capable of alleviating a burden on a caregiver which could arise when a plurality of types of notification target motions is detected during a short time period. A motion detection system (300) includes: an acquisition unit (52) for acquiring motion data indicating a motion of a person; a detection unit (150) for detecting a predetermined motion of the person using the motion data; a selection unit (160) for, when a plurality of types of output candidate motions is detected by the detection unit (150) during a predetermined time period, selecting an output target motion from among the output candidate motions such that types of the output candidate motions are made fewer than the plurality of types; and an output unit (170) for outputting the output target motion selected by the selection unit (160).