Abstract
　The main objective of this paper is to investigate the reason why the composite breakwater has been exclusively used in Japan since around l900. In the construction of Yokohama harbor, the composite brakwater was first introduced in 1889 by Palmer, a hired English foreigner. In the Cabinet council meeting pf the prime Minister Kuroda in March, 1889, the construction project Affairs. This decision did not reflecty the results of the judging committee in the Ministry of Home Affairs. From the viewpoints of revision of an unequal treaty, that is quite political. Moreover, the construction had been managed not by the Ministry of Home Affirs but the Ministry of Finance. Since the late period of Meiji (about 1990), the composite breakwater which has been throgh many improvements has been authorized and constructed in every harbor in Japan.

【キーワード】：防波堤, 混成堤, 　傾斜堤, 海岸災害, お雇い技師, 不平等条約改正, 築港, 災害技術史

*京都大学防災研究所 Disastr Prevention Research Institute, Kyoto Univ.