A face authentication system including a storage to store a face image of each of a plurality of persons who are permitted to enter in advance and information on a zone; an image processing unit to detect a face of at least one person in an image captured by at least one camera having identification information, and generate a face cut-out image of the at least one person; a zone determination unit to determine a zone where a person in the face cut-out image is captured; a collation unit to collate the face cut-out image with the face image of each of the plurality of persons; and an output control unit to, when it is determined that there is not a face of a person appearing in the face cut-out image, superimpose a detection frame indicating a face of a person who is not permitted to enter the zone.