SUMMARY OF THE INVENTION It is an object of the present invention to provide a self-lifting device for a self-lifting device that automatically lifts a self-lifting barrel while maintaining proper gripping force in response to a change in the thickness of the self-lifting barrel. To achieve the above object, according to the present invention, there is provided a gear device comprising: a gear (110) for placing a rod to be lifted on a surface facing each other and lifting the rod while rotating in opposite directions by rotation； A rotation rod 120 coupled to the axis of the gear 110 to transmit rotational force； A rotating motor (not shown) connected to the rotating rod 120 to provide rotating force to rotate； A cylindrical space for receiving a bearing 130 inserted into the rotary rod 120 is provided in the inside of the rotary rod 120, a housing is coupled to the rotary motor on one side, and a guide groove 151 A pair of horizontal moving parts 100, A guide 700 inserted into the guide groove 151 of the horizontal movement unit 100 and guided to move in the horizontal direction； A pair of links 300 each connected to the pair of horizontal moving parts 100； A cylinder 510, an oil pump for supplying oil into the cylinder 510, A lever (5) for regulating the supply of oil to the cylinder (510)； A piston 540 reciprocating along the axis of the cylinder 510 and passing through the inside of the cylinder 510 and having an oil seal on an outer circumferential surface contacting the inner region of the cylinder 510 and an inner circumferential surface passing through the piston, The piston rod 530 is inserted into a through region of the bearing 150 and is coupled to one side of the piston rod 530 and connected to the pair of links 300, And a spring 550 which is positioned at the other side of the piston rod 530 and is fixed to the nut 560 so as not to be separated by the actuator 520. [ A self-lifting device is provided.본 발명의 목적은 봉줄의 굵기나 표면이 일정하지 않아도 봉줄의 굵기 변화에 자동으로 대응하여
