Closed U shape trough rib is widely used because it is strong in stiff ness as stiffener of deck plate, uniformly in distribution of loading, and light in weight of member in steel box girder bridge. It also prevented rust because of its perfectly closed section. Welding distortion becomes little since welding process is reduced in elevated bridge and long span of the steel box girder bridge with the closed U shape trough rib. Torsional moment occurs in cross section of steel box girder bridge. Resistance and shearing stress of torsion are compared and examined in steel box girder when opened rib and closed U shape trought rib are attached at the steel deck plate respectively. The test specimen which is the closed U shape trough rib is manufactured as full scale model and carried out by static bending test and fatigue test. The stress behavior is examined on cross section of the close U shape trough rib from the static bending test and the fatigue lest. The stress of closed U shape trough rib is obtained from 3 dimensional stress analysis by finite element method. The results obtained from this study are as follows: The torsion is almost burdened on the steel box girder when the opened rib and the closed U shape trough rib are attached at the box girder respectively. The torsinal resistance of closed U shape trough rib is larger than that of opened rib when opened rib and U shape trough rib are attached to deck plate in the steel box girder respectively. The shear lag by shearing distortion occurs not only corner of the U shape trough rib in the static bending test and the fatigue test, but also in the 3 dimensional stress analysis by the finite element method. Accordingly, it is necessary to take the counterplan for the shear lag in case the closed U shape trough rib is used as the stiffener of box girder.