1. A personal authentication method using biological information, wherein the method is performed on an authentication apparatus, the method comprising the steps of: maintaining a biological feature database storing for each user including at least a person to be authenticated: (1) feature information of a plurality of categories of biological features; and (2) resource accessibility potential information table on the relationship between: (a) combination of the plurality of categories of biological features and (b) authentication precision which is a probability that others are not accepted as the user, the probability being obtained by trial-calculating FAR (False Acceptance Rate); having the person to be authenticated select at least two of the categories of biological features; retrieving authentication precision for the authentication from the biological feature database using the selected combination of categories of biological features as a query; determining whether or not the retrieved authentication precision exceeds a threshold required for purposes of authentication, before allowing the user to enter actual feature information into an authentication device; requesting the person to be authenticated to reselect at least one of the categories of biological features when the retrieved authentication precision fails to exceed the threshold; allowing the person to be authenticated to enter actual feature information of the selected categories of biological features into the authentication device only when the authentication precision exceeds the threshold; and performing authentication of the person to be authenticated by comparing the entered feature information and the feature information of the corresponding categories of biological features stored in the biological feature database.