A biometric authentication apparatus includes a part to retain first biometric data items extracted from living body parts of a user in correlation with the collation order of the first biometric data items; a part to acquire a second biometric data item from the user, to compare and collate the acquired second biometric data item with the first biometric data items in descending order of their collation priorities based on the collation order, and to determine that the user has been successfully authenticated in response to detecting one of the first biometric data items whose match rate with the second biometric data item exceeds a predetermined value; and a part to change the collation order in response to detecting, from the state of usage of the one of the first biometric data items, that the user has steadied at a change of her/his living body part to use for authentication.