A gigantic tsunami was generated in the Indian Ocean Earthquake on December 26, 2004. Thetsunami attacked and gave the devastated damages in the coastal areas facing to the Indian Oceanincluding the Northern Sumatra, West Malaysia, South Thailand, Sli Lanka, South India etc. A fieldsurvey was carried out in the coastal area in the South Thailand to mainly investigate the beacherosion due to tsunami flow. The paper describes the characteristics of beach erosion observed inthe field. The beaches were heavily eroded in the Khao Lak beach where the tsunami run-up heightbecame more than 10m. A short survey in Banda Aceh city coast, Indonesia is introduced in thepaper.