In Japan, various rockfall protection structures are constructed along mountainous and coastal roads to protect transportation networks from rockfall. As one of these structures, there is the conventional rockfall protection fence which is composed of H-shaped steel posts, wire ropes, diamond-shaped wire mesh, and clearance-keeping strips for the ropes. However, the actual fences sometimes suffer damages due to local buckling of the posts and/or fracture of the wire mesh, which have not been considered in the design specification. To restrain these damages, it is essential to investigate the impact-resistant behavior of the fences by conducting not only impact loading tests but also numerical analysis. From this point of view, in this paper, a three-dimensional elasto-plastic response analysis method was proposed and its applicability was investigated by comparing with the impact loading test results for a full-scale conventional rockfall protection fence. From this study, the time histories of the impact force and the horizontal movement of the steel weight, and the tensile force applied in the wire ropes can be appropriately evaluated by using the proposed analysis method.