Since the UD direction ground motions of the Hyogoken-nambu and Niigataken-chuetsu earthquakes were very large, it suffered the seismic damage that earth structures was very enormous. However, the effects which vertical seismic motion exerts on the destruction of embankment aren't taken sufficiently into account in the seismic design of the earth structures, So, in this study, the simple and easy calculation method of seismic response calculation that the vibration characteristics in the horizontal and vertical direction of embankments were taken into consideration at the same time is proposed. Then, the modified Newmark method that response characteristics in both directions of embankments were taken into consideration is proposed.