PURPOSE: To facilitate spiral connection of screw members by screwing a female screw member around a male screw member after both of them are placed in mutual racing.

CONSTITUTION: An air motor 23 is operated to race a supplementary electrode 8 through a clamp mechanism 25. After a prescribed number of racing a screwing apparatus 21 is lowered in an elevator frame 43 at the time when a large torque is generated by means of an inertia due to the large mass of the electrode 8, and a male screw part 8A of the electrode 8 is screwed into a female screw part 4A of an electrode 4. Thus the electrode 8 is jointed to the electrode 4. Thus screwing connection between the female screw member and the male screw member large masses can be carried out easily in a short time by using an air motor of a small output, and even in the case of a high temperature apparatus such as an electric stove, there is no danger of ignition and members connection can safely be performed.