A mobile information terminal that acquires user gripping feature samples when being gripped and that performs user authentication, the terminal comprising: a mode acquisition section adapted to acquire a mode which is a classification of situations of use of the mobile information terminal; a gripping-feature sample acquisition section adapted to acquire the user gripping feature samples; a switch adapted to switch the mobile information terminal between a learning state and a user authentication state; a template learning section adapted to learn a user authentication template in each mode by using the user gripping feature samples acquired by the gripping-feature sample acquisition section, when the mobile information terminal is in the learning state; an authentication section adapted to compare user gripping feature samples acquired when the mobile information terminal is in the user authentication state, with the learned user authentication template to perform the user authentication; and a locking section adapted to lock some or all of the functions of the mobile information terminal when the user authentication fails; characterized in that: the mobile information terminal further comprises a sample filling section adapted to, when the mobile information terminal is in the learning state of the user authentication template and the number of user gripping feature samples acquired in a mode does not reach a predetermined number, fill in the lacking user gripping feature samples in the mode, hereinafter this mode is referred to as feature-lacking-mode, with user gripping feature samples acquired in a mode which is similar to the feature-lacking-mode. a mode acquisition section adapted to acquire a mode which is a classification of situations of use of the mobile information terminal; a gripping-feature sample acquisition section adapted to acquire the user gripping feature samples; a switch adapted to switch the mobile information terminal between a learning state and a user authentication state; a template learning section adapted to learn a user authentication template in each mode by using the user gripping feature samples acquired by the gripping-feature sample acquisition section, when the mobile information terminal is in the learning state; an authentication section adapted to compare user gripping feature samples acquired when the mobile information terminal is in the user authentication state, with the learned user authentication template to perform the user authentication; and a locking section adapted to lock some or all of the functions of the mobile information terminal when the user authentication fails; characterized in that: the mobile information terminal further comprises a sample filling section adapted to, when the mobile information terminal is in the learning state of the user authentication template and the number of user gripping feature samples acquired in a mode does not reach a predetermined number, fill in the lacking user gripping feature samples in the mode, hereinafter this mode is referred to as feature-lacking-mode, with user gripping feature samples acquired in a mode which is similar to the feature-lacking-mode. the mobile information terminal further comprises a sample filling section adapted to, when the mobile information terminal is in the learning state of the user authentication template and the number of user gripping feature samples acquired in a mode does not reach a predetermined number, fill in the lacking user gripping feature samples in the mode, hereinafter this mode is referred to as feature-lacking-mode, with user gripping feature samples acquired in a mode which is similar to the feature-lacking-mode.