An object detection unit 60 detects, from video data indicating the actions of a person: appearance features pertaining to objects in the vicinity of the person and the appearance of the person; person region information pertaining to a region indicating the person; and object region information pertaining to a region indicating the object. An action features extraction unit 62 extracts action features pertaining to the actions of the person, on the basis of the video data and the person region information. A relationship features extraction unit 64 extracts relationship features indicating the relationship between the object and the person, on the basis of the object region information and the person region information. An abnormality determination unit 66 determines whether or not the actions of the person are abnormal, on the basis of the appearance features, the action features, and the relationship features.