An action detection system that can alleviate false notifications that occur in unexpected situations is provided. An action detection system (300) includes an acquisition unit (150) acquiring an image, a storage unit storing a state transition table (222) for specifying transition relationship between a plurality of types of actions, notification action information (226) defining a notification target action, and a current action (224) of the care-recipient, an action detection unit (255) for specifying a transitionable action to which transition can be made from the current action (224) on the basis of the state transition table (222), and detecting the transitionable action on the basis of the image, a transition control unit (260) for updating the current action (224) to a new action detected, a notification unit (270) for, in a case where the new action is the notification target action, providing notification of a type of the new action, and an update unit (285) for, in a case where a first condition defined in advance indicating that it is not suitable to determine the type of the action of the care-recipient is satisfied, reducing the type of the notification target action and updating the transition relationship of the state transition table (222).
