A monitoring apparatus (102) includes a detection unit (103) that detects a person P taking a predetermined action, based on an image being acquired by imaging an inspection area R, and an output unit (104) that outputs detection information relating to the person P being detected. For example, the predetermined action includes at least one of a first action being decided in relation to an item, a second action being decided in relation to a visual line of a person, a third action being decided in relation to a movement (including staying) of a person, a fourth action being decided in relation to entry in/exit from a predetermined area, and the like.