A person authentication method comprising: obtaining, from a medium carried by a first person who passes through a first position, first information indicating gender and age of the first person; setting, as a first authentication operation, an authentication operation to retrieve, from a memory, a plurality of face images of second persons who have the same gender or the same age as specified in the first information, compute a degree of similarity between the plurality of face images retrieved from the memory and a first image obtained by capturing the first person passing through the first position by a camera, and determine if the degree of similarity exceeds a predetermined threshold; performing the first authentication operation with respect to the first person whose face image is included in the first image obtained by capturing the first person passing through the first position by the camera; when the degree of similarity exceeds the predetermined threshold, determining that the first person is a same person whose first information has been obtained from the medium; storing history information of the first authentication operation in a corresponding manner to the first identification information in a first memory, if the first person is successfully authenticated in the first authentication operation; obtaining, from the medium carried by the first person who passes through a second position, second identification information of the person; performing a re-authentication operation with respect to the first person with a face image included in a second image that is taken by capturing the first person passing through the second position; and retrieving, from the first memory, the history information matching with a predetermined re-authentication history condition, wherein the re-authentication operation is performed only when the second identification information matches with the first identification information that is stored in the first memory in a corresponding manner to the history information matching with a predetermined re-authentication history condition. obtaining, from a medium carried by a first person who passes through a first position, first information indicating gender and age of the first person; setting, as a first authentication operation, an authentication operation to retrieve, from a memory, a plurality of face images of second persons who have the same gender or the same age as specified in the first information, compute a degree of similarity between the plurality of face images retrieved from the memory and a first image obtained by capturing the first person passing through the first position by a camera, and determine if the degree of similarity exceeds a predetermined threshold; performing the first authentication operation with respect to the first person whose face image is included in the first image obtained by capturing the first person passing through the first position by the camera; when the degree of similarity exceeds the predetermined threshold, determining that the first person is a same person whose first information has been obtained from the medium; storing history information of the first authentication operation in a corresponding manner to the first identification information in a first memory, if the first person is successfully authenticated in the first authentication operation; obtaining, from the medium carried by the first person who passes through a second position, second identification information of the person; performing a re-authentication operation with respect to the first person with a face image included in a second image that is taken by capturing the first person passing through the second position; and retrieving, from the first memory, the history information matching with a predetermined re-authentication history condition, wherein the re-authentication operation is performed only when the second identification information matches with the first identification information that is stored in the first memory in a corresponding manner to the history information matching with a predetermined re-authentication history condition.