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.