To prevent rust and facilitate the maintenance work by forming a part supporting a girder structure by a support shoe to shape a boxed girder structure and forming other intermediate girder parts to have a I-shaped girder structure and constituting the underface plate of the I-shaped girder with decorative plates.

A part supported by a support shoe 2 is formed to have a boxed girder 3 structure and other intermediate parts having the underface members of decorative plates 4 are formed to have an I-shaped girder structure, in a girder 1 of a bridge. Since the boxed girder structure 3 requires necessary rigidity and fatigue strength, it is constituted of an enclosed structure made of a steel box girder 3 to completely keep out rainwater or the like and prevent rust. The I-shaped girder structure is also an enclosed form with the decorative plate 4 at the underface to prevent penetration of rainwater and prevent rust. The boxed girder 3 structure and the I-shaped girder structure are combined and the decorative plate 4 is used at the underface of the I-shaped girder to make a hybrid girder 1. In this way, the rigidity is kept and rust is prevented and further, the maintenance work is facilitated.