The specifications for highway bridges require cushioning material to be installed on bridge restrainers to reduce seismic impact force; although no clear standard design method of cushioning material is provided in the current specification. Thus, it seems to have a potential for making the design of bridge restrainers more appropriate if the evaluation of cushioning effect could be more quantitatively. Therefore, weight-drop tests were conducted on cushioning rubber pieces to get fundamental data on cushioning characteristics. In this test, it was focused on rubber pieces' shape, hardness and confining conditions. It was obtained that cushioning characteristics would be significantly affected by the rubber pieces' shape and confining conditions.