A mobile information terminal (550,500') that acquires a gripping-feature sample when the mobile information terminal (550, 500') is gripped, so as to perform user authentication, comprising: a gripping-feature sample acquisition unit configured to acquire a gripping-feature sample; an environmental sensor group that includes one or more sensors that acquire environmental information, which is one or more combinations of activated application information, gravity direction information, vibration information, shock detection information, angle information, angular velocity information, angular acceleration information, sound information, illuminance information, and position information, and output a signal of the environmental information as an environmental signal; a terminal status detection unit configured to acquire the environmental signal and detect one or more combinations of terminal status from the combination of active state application, motion states, operation postures, brightness, and position information as environmental states; a template storage unit configured to store a user authentication template that fits to each of the environmental states; a template selection unit configured to acquire the environmental state that is detected, so as to select a user authentication template that fits to the corresponding environmental state; a user authentication unit that performs user authentication by collating the gripping-feature sample that is acquired with the user authentication template that is selected, and outputs a corresponding user authentication result; a user authenticity level monitoring unit that acquires the user authentication result, outputs a sensor power source OFF signal when a user authenticity level, which varies in accordance with the user authentication result, varies to exceed a threshold value that is predetermined to correspond to each sensor, and outputs a sensor power source ON signal when the user authenticity level varies to fall below the threshold value; and a power source control unit that halts energization to a sensor that corresponds to the threshold value when the power source control unit acquires the sensor power source OFF signal, and energizes a sensor that corresponds to the threshold value when power source control unit acquires the sensor power source ON signal. a gripping-feature sample acquisition unit configured to acquire a gripping-feature sample; an environmental sensor group that includes one or more sensors that acquire environmental information, which is one or more combinations of activated application information, gravity direction information, vibration information, shock detection information, angle information, angular velocity information, angular acceleration information, sound information, illuminance information, and position information, and output a signal of the environmental information as an environmental signal; a terminal status detection unit configured to acquire the environmental signal and detect one or more combinations of terminal status from the combination of active state application, motion states, operation postures, brightness, and position information as environmental states; a template storage unit configured to store a user authentication template that fits to each of the environmental states; a template selection unit configured to acquire the environmental state that is detected, so as to select a user authentication template that fits to the corresponding environmental state; a user authentication unit that performs user authentication by collating the gripping-feature sample that is acquired with the user authentication template that is selected, and outputs a corresponding user authentication result; a user authenticity level monitoring unit that acquires the user authentication result, outputs a sensor power source OFF signal when a user authenticity level, which varies in accordance with the user authentication result, varies to exceed a threshold value that is predetermined to correspond to each sensor, and outputs a sensor power source ON signal when the user authenticity level varies to fall below the threshold value; and a power source control unit that halts energization to a sensor that corresponds to the threshold value when the power source control unit acquires the sensor power source OFF signal, and energizes a sensor that corresponds to the threshold value when power source control unit acquires the sensor power source ON signal.