To lower the construction cost, and to shorten the construction period by eliminating construction, loading an removal of a temporary hoisting part to be finally eliminated.

Both ends of an extra-large girder 10 are formed of a lower beam end 11 extended to the full length of the extra-large girder 10 and an upper beam end 12 shorter than the lower beam end 11, and a girder corresponding to the residual length of the upper beam end 12 is previously constructed as a hoist beam 13 at an extra-large girder 10 fitting part of a main pillar. Continuously, a hoisting jack 16 is fitted to the hoist beam 13, and the lower beam end 11 of the extra-large girder 10, which is positioned under the hoist beam 13 in the vertical direction, is hoisted so as to be raised to a predetermined position. Furthermore, the upper girder end 12 and the lower beam end 11 are connected to fitting parts 13, 14, which are provided in the main pillar 1, by each joint 19a, 19b.