This paper describes two kinds of caisson technology (caisson type structure and pneumatic caisson method) which spread quickly in ports construction, such as a breakwater and a quay, in the Showa prewar term from the second half of Meiji. As the method of research, thinking of an engineer is analyzed by making free use of technical papers and textbooks of those days. And it is going to clarify about the circumstances of adoption of two kinds of caisson technology. However, this paper does not emphasize on discovery of the new fact, and it is establishing the historical review of technical of caisson. And it is another purpose to list the caisson structure which was almost uninterested until now on the civil engineering heritage.