In this report, the effectiveness of decreasing of tsunami force due to seawall was investigated by physical experiments. The seawall with 30cm height was used in this study, and solitary waves and sin waves were attacking on the building behind the seawall. Three different situations of seawall were tested. One is without seawalls, the other is with seawalls, and those seawalls are falling or rigid. The results show that the relationship between the Froude number and the coefficient of pressure are based on the Bernoulli's principle. When the tsunami height is almost same as the height of seawall, the pressure on the buildings behind seawalls are getting smaller than that without seawalls. The speed of falling of seawall is affected on the pressure on the building. If the speed is getting higher, then the pressure is getting larger.
