The Shishin-den, the supreme hall of the Imperial Domicile (Dairi-seiden, 内裏正殿) in Heian-kyu, is described as Zen-den (前殿, the State Chamber) in the Nihon-kouki (one of the Rikkoku-shi, the authentic chronicles of Japan compiled by the central government between the 8th and the 9th centuries). The terms of Zen-den are also recorded in the Nihon-shoki and the Shoku-nihongi (one of the Rikkoku-shi) ; therefore the Shishin-den is supposed to have followed not only Dairi-seiden, but also Zen-den of the former ages. The aim of this study is to show the architectural characteristics of the original Shishin-den by investigating the histories of Zen-den and Dairi-seiden, on the basis of the Rikkoku-shi and the excavation of the ancient imperial palace site. In order to study these facts, however, it is necessary to show the relations between Zen-den and Daigoku-den (大極殿), Daian-den (大安殿), Chodo (朝堂, the Halls of State), which were the central buildings in the palace grounds. Therefore, another aim of this study is to investigate the relations between those buildings in each palace from Asuka-kiyomihara-kyu to Heian-kyu. As the terms of Zen-den and Chodo recorded in the Rikkoku-shi were referred to chinese terminology, we'd like to study the origin of those buildings and definitely show their characteristics by comparing them with the examples of Qiandian (前殿) and Zhaotang (朝堂) of the ancient imperial palace in China. On this paper, Part 1, the State Chamber and the Halls of State of Asuka-kiyomihara-kyu and Fujiwara-kyu have been investigated. The results obtained from this study are as follows : 1) Daigoku-den described in the chapter of the Emperor Tenmu of the Nihon-shoki is supposed to have been the identical building with Daian-den of Asuka-kiyomihara-kyu which was the supreme hall of Nai-cho, or the residential part of the Imperial Palace. 2) The original Daigoku-den in Japan was built at Fujiwara-kyu as Zen-den, that is, the State Chamber of Chucho, or the formal part of the Imperial Palace, imitating Taijidian (太極殿) in Chang'an capital in the Tang age. 3) Both Chodo of Asuka-kiyomihara and Fujiwara Imperial Palace were used not only as halls for official ceremonies and banquets, but also as chambers for administering State affairs.