In order to establish the design method of the shear connectors, which is taken into account not only the longitudinal shear force but also the pull-out force due to the transverse bending moment of the slab, the loading test using full-scale models was carried out. The headed stud was selected as the shear connector, which has been generally used by reason of excellent executivity and the independent of the direction of the longitudinal shear force. In this paper, through the experimental study, we proposed the rational arrangements of the headed studs on the upper flange near the vertical stiffener of the steel girder in composite two-I-girder bridges.