A personal authentication method capable of selecting types of biological
information used for authentication flexibly depending on the user and
the environment is provided. During registration, a plurality of types of
biological information are acquired from the user, feature information is
extracted from the acquired biological information, and authentication
precision is estimated for each combination of pieces of feature
information. During authentication, at least one type of biological
information is acquired from the user, feature information is extracted
from the acquired biological information, authentication is performed by
comparing the acquired feature information with the feature information
extracted from the biological information during registration, and
operation of the user is controlled according to the authentication
precision.