A biometric authentication apparatus comprising: a comparator configured to perform authentication of a user by comparing biological information read from the user with registered biological information registered in a storage in advance; a high accuracy comparator configured to compare the read biological information with the registered biological information with a higher accuracy than the comparison using the comparator when the comparator fails to authenticate the user; and a comparison result storage configured to record a comparison result obtained by the high accuracy comparator in the storage, wherein the high accuracy comparator is further configured to divide an area used in the comparison by the comparator into a plurality of parts, and compare the biological information and the registered biological information by processing a partial comparison to perform comparison for each of the plurality of parts, wherein the high accuracy comparator is configured to calculate a vector representing an incident direction of external light in the biological information, based on a degree of similarity for each of the plurality of parts in the partial comparison with the registered biological information, and stores the calculated vector in the storage, and wherein the biometric authentication apparatus further comprises an analysis unit that displays, on a display, a history table including a plurality of external light error rates corresponding to different time periods, each of the external light error rates is a ratio of a number of errors due to the external light to a total number of times of authentication performed during each of the different time periods, and including the average of the external light directions for each of the different time periods. a comparator configured to perform authentication of a user by comparing biological information read from the user with registered biological information registered in a storage in advance; a high accuracy comparator configured to compare the read biological information with the registered biological information with a higher accuracy than the comparison using the comparator when the comparator fails to authenticate the user; and a comparison result storage configured to record a comparison result obtained by the high accuracy comparator in the storage, wherein the high accuracy comparator is further configured to divide an area used in the comparison by the comparator into a plurality of parts, and compare the biological information and the registered biological information by processing a partial comparison to perform comparison for each of the plurality of parts, wherein the high accuracy comparator is configured to calculate a vector representing an incident direction of external light in the biological information, based on a degree of similarity for each of the plurality of parts in the partial comparison with the registered biological information, and stores the calculated vector in the storage, and wherein the biometric authentication apparatus further comprises an analysis unit that displays, on a display, a history table including a plurality of external light error rates corresponding to different time periods, each of the external light error rates is a ratio of a number of errors due to the external light to a total number of times of authentication performed during each of the different time periods, and including the average of the external light directions for each of the different time periods.