It is provided an authentication system comprising: an input device; an image pickup device for picking up an image of the living body; an image processing unit for processing the image picked up by the image pickup device; a storage device for storing a plurality of pieces of first feature data and a plurality of pieces of second feature data; and a matching processing unit for checking input data, which indicates features of a living body picked up by the image pickup device, against each of the plurality of pieces of first feature data and each of the plurality of pieces of second feature data. Each of the plurality of pieces of second feature data is data that is smaller in size than each of the plurality of pieces of first feature data and that includes at least a part of the features of the living body.