The invention provides an actuating device capable of locking and unlocking PARK of a speed selection handle arranged on a stepped shifter. The actuating device includes a locking box, i.e. a movement locking box (10), an unlocking handle, i.e. a collapsible handle (20), and an electromagnetic unit (15, 25). When the locking box is not pressed against the brake pedal of the vehicle, the locking box stops the movement of the speed selection handle (1). When the locking box is pressed against the brake pedal of the vehicle, the collapsible handle drives the movement locking box (10) to leave away from the speed selection handle (1), so the movement of the speed selection handle is released. The electromagnetic unit is controlled by the movement locking box which is pressed against the brake pedal, and allows the position of the locking box which stops the movement of the speed selection handle to be converted into the position of the locking box which releases the movement of the speed selection handle.