An authenticating apparatus comprising: receiving means that receives an image region as an authentication target read from a surface of a target object possessed by a user together with an authentication request from the user; comparing means to compare the image region as the authentication target with a plurality of previously stored reference image regions read from respective surfaces of a plurality of target objects; identifying means that identifies a position corresponding to the image region as the authentication target and one reference image region corresponding to the image region as the authentication target in the plurality of previously stored reference image regions; and authenticating means that executes authentication in response to the authentication request based on the identified position, wherein: the identifying means identifies a position in the one reference image region corresponding to the image region as the authentication target in the plurality of reference image regions, and in that the authenticating means further comprises authentication request determining means that determines whether or not the authentication request is valid based on whether or not the identified position in the reference image region is included in a compared image region including a position corresponding to a read image region received in past, wherein, if the authentication request determining means has determined that the authentication request is not valid, the authenticating means determines authentication failure in response to the authentication request, and wherein, if the authentication request determining means has determined a predetermined number of times that the authentication request received from the same user by the receiving means is valid, the authenticating means determines authentication success in response to the authentication request received from the user. receiving means that receives an image region as an authentication target read from a surface of a target object possessed by a user together with an authentication request from the user; comparing means to compare the image region as the authentication target with a plurality of previously stored reference image regions read from respective surfaces of a plurality of target objects; identifying means that identifies a position corresponding to the image region as the authentication target and one reference image region corresponding to the image region as the authentication target in the plurality of previously stored reference image regions; and authenticating means that executes authentication in response to the authentication request based on the identified position, wherein: the identifying means identifies a position in the one reference image region corresponding to the image region as the authentication target in the plurality of reference image regions, and in that the authenticating means further comprises authentication request determining means that determines whether or not the authentication request is valid based on whether or not the identified position in the reference image region is included in a compared image region including a position corresponding to a read image region received in past, wherein, if the authentication request determining means has determined that the authentication request is not valid, the authenticating means determines authentication failure in response to the authentication request, and wherein, if the authentication request determining means has determined a predetermined number of times that the authentication request received from the same user by the receiving means is valid, the authenticating means determines authentication success in response to the authentication request received from the user. the identifying means identifies a position in the one reference image region corresponding to the image region as the authentication target in the plurality of reference image regions, and in that the authenticating means further comprises authentication request determining means that determines whether or not the authentication request is valid based on whether or not the identified position in the reference image region is included in a compared image region including a position corresponding to a read image region received in past, wherein, if the authentication request determining means has determined that the authentication request is not valid, the authenticating means determines authentication failure in response to the authentication request, and wherein, if the authentication request determining means has determined a predetermined number of times that the authentication request received from the same user by the receiving means is valid, the authenticating means determines authentication success in response to the authentication request received from the user.