A mobile terminal includes a processor shifting a state between a first restricted state for restricting a key operation except for at least a code inputting operation, a second restricted state for restricting a key operation including at least said code inputting operation, and a unrestricted state for making a key operation unrestricted. The processor selects the unrestricted state when a code input by the code inputting operation in the first restricted state is a preset code. Furthermore, whether or not the number of executions of the code inputting operation in the first restricted state is above a threshold value is repetitively determined, and if the determination result is negative, the first restricted state is selected while if the determination result is affirmative, the second restricted state is selected. Then, a possibility of a key operator being a qualified person is repetitively determined, and as the possibility is high, the threshold value is made large.