1. An authentication system for authenticating a person-to-be-authenticated, comprising: a first photographing section, which is provided in a route passed by the person-to-be-authenticated, operable to photograph the person-to-be-authenticated; a first authentication section operable to perform a first authentication of the person-to-be-authenticated photographed by said first photographing section; a second photographing section, which is provided at a location through which the person-to-be-authenticated passes, operable to photograph the person-to-be-authenticated, wherein said second photographing section is located downstream of said first photographing section in the route passed by the person-to-be-authenticated; and a second authentication section operable to authenticate the person-to-be-authenticated by comparing an image of the person-to-be-authenticated photographed by said first photographing section with an image of the person-to-be-authenticated photographed by said second photographing section.