A mobile information terminal that can authenticate an authorized user by using behavioral features acquired when the user makes small movements in a limited movable range. The mobile information terminal includes a gripping feature sensor that acquires gripping features; a behavioral feature sample acquisition section that acquires time-series data of gripping features in a fiddling session as samples of behavioral features; a switch that puts the mobile information terminal into either a learning mode or an authentication mode; a template learning section that learns an authentication template by using the samples of behavioral features when in the learning mode; an authentication section that authenticates the user by comparing the samples of behavioral features with the learned authentication template when in the authentication mode; and an unlock section that unlocks all or some of the functions of the mobile information terminal when the authentication succeeds.