Abstract
In studying the history of the construction of rice-fields in the Kochi Plains, I divided it into the following four periods; the Primitive Age, the Remote Age, the Medieval Feudal Age and the Modern Feudal Age. Especially I took up the construction of the irrigation ditches as the fundamental condition for the cultivation of rice-fields. Furthermore, laying stress on the relation to the administrative power which made the construction of the irrigation ditches possible, I summed up the features of each period as follows-the Primitive and the Medieval as the constructive period of the irrigation ditches on a small scale by separated power, and, the Remote and the Modern as the constructive period of the irrigation ditches on a large scale by concentrated power.
