If a gigantic tsunami attacks in coastal area, most kinds of structures such as residential houses, industrial plant and cargo transporter would be broken down. Since the best way to preserve the human life from the tsunami is that people run away to a higher place as much as possible, a refuge building in coastal region may exert great effect for saving life. In order to evacuate people safety in the buildings, structure of the building must hold against the gigantic tsunami load. Therefore, it is necessary to estimate the tsunami force on the structure accurately. The objective of this study is to investigate tsunami forces on the structures in coastal area. Hydraulic experiment is carried out to clarify the characteristics of tsunami force, especially the relationship to the agreement of houses and the distance from seawall.