It is provided a biometric authentication system, which is configured to execute authentication by using registered biometric information, the biometric authentication system comprising: a light source unit configured to irradiate a living body with light; an image pickup unit configured to photograph a vessel image with light radiated from the light source unit and transmitted through the living body; a control unit configured to generate authentication biometric information from the vessel image photographed by the image pickup unit; a category selection unit configured to select a category that corresponds to the authentication biometric information, based on supplementary information including information that has been obtained about a position and posture of the living body at timing of photographing the vessel image; and an authentication unit configured to execute authentication processing by comparing registered biometric information of the selected category and the authentication biometric information.