PURPOSE: To speed up unlocking operation by driving a driving plate rotationally driving a rotary body fixed in a rotary shaft of a lock directly/indirectly by means of an electric motor and controlling rotation of the motor by means of an operation board.

CONSTITUTION: In a lock box 2 for an entrance door, a safe door or the like, a driving plate 14 driving a rotary body 12 fixed in a rotary shaft 13 of a lock is rotated by means of an electric motor 15, so that dial graduation setting in unlocking can be carried out by means of the motor 15. That is, a ten key 18 and the like on an operation board 17 is operated for transmitting a desired data signal to a control unit 16, and on the basis of this signal, computing process is carried out for transmitting a control signal to the motor 15, so that rotation of the motor 15 is controlled for rotating a tumbler 7, and then, an unlocking groove in the tumbler 7 is brought to confomity for unlocking. In case of a failure in the motor 15, the tumbler 7 can be operated manually. In this way, unlocking operation can be carried out quickly.