A mobile information terminal including a gripping-feature sample acquisition unit to acquire a gripping-feature sample, one or more environmental sensors outputting an environmental signal, a terminal status detector to acquire the environmental signal and detect a terminal status, a template selection unit to select a user authentication template fitting the detected terminal status, a user authentication unit collating the acquired gripping-feature sample with the selected user authentication template and outputting a user authentication result, a user authenticity level monitor that outputs a sensor power source OFF signal when the user authenticity level exceeds a threshold value and outputs a sensor power source ON signal when the user authenticity level falls below the threshold value, and a power source control unit halting energization to a sensor when acquiring the sensor power source OFF signal, and energizing a sensor when acquiring the sensor power source ON signal.