Concrete-steel composite members are formed by bonding a steel component, such as an I-section beam, to a concrete component, such as a reinforced concrete slab, so that the two components can act as a unit. The use of such type of composite member becomes main stream of construction technology since it provides efficient load resisting mechanism in structural system. In a composite member, bond between steel and concrete is a crucial factor for the composite action. Usually this bond behavior is achieved by installation of mechanical device so called shear connector. The composite action can be divided into two categories (i.e., full and partial) depending on the shear strength of mechanical shear connector embedded in the concrete, i.e., understanding of shear load resisting mechanism is necessary to develop a new shear connector for better, wider and more efficient application of composite action. For this purpose, the push-out tests are performed for the evaluation of several existing shear connectors including carefully designed perforated shear connector with flange head. One of the purposes of this experimental research is to define the shear resisting mechanism of the proposed new type shear connector. The experimental results show that the degree of composite action using perforated shear connector with flange head is superior to those of existing shear connectors such as a general headed stud, perfobond, etc. The experimental parameters, such as the number of perforated holes, the distance between perforated holes, and the height of shear connector, are carefully chosen for the verification of their effect on the capacity of shear resistance. From this experimental investigation it was found that the mechanical performance of proposed shear connector was efficient as a rigid shear connector.