The importance of grasping the actual conditions of beach cbange during a storm surge has been recognized. Until now，however，such a field survey or a research is not carried out，because it is generally impossible to have topographic data concerning to tbe beach topography before an attack of storm surge. On September 24，1999，the typhoon No. 9918 attacked and induced the huge storm surge at tbe coasts in the west of Japan. Fortunately，the monitoring surveys of beach process have been being conducted periodically on tbe Nijigahama Coast，Yamaguchi prefecture，since 1995，and the topographic data of beach on tbe day of two weeks before tbe storm surge have been obtained. Then，just after tbe stom surge，we surveyed the beacb topography and the elevations of inundation traces from a viewpoint of beach deformation. By comparing the pre-storm data and the post-storm ones，the actual condition of beach changes during the storm surge. The main conclusions are as follows；
(1)The waves run up beyond the back-shore，of which profile is convex upward，inducing the inundation in the rear area during the high water level.
(2)The up-rush of sea water took the sand from tbe foreshore and transported it to the rear area.
(3)The back-Shore covered with vegetation stood up to the overflow with keeping its profile，while the back-shore without vegetation was eroded about 40 cm in elevation.