For the effective finite element analysis of the structures including material interfaces or contact surfaces, interface elements are proposed. Most of early works in this problem require not only iterative computation but also complex formulation because of the kinematic nonlinearities caused from the discontinuous behavior and the stress concentration phenomena. The proposed elements, however, are consistently formulated using relative displacements and tractions between top and bottom regular finite elements. The effectiveness of these elements are shown by solving various numerical sample problems including an leaf spring and comparing with results of general finite element analysis. As a result, more stable solutions are conveniently obtaines using interface elements than regular finite elements.