What kind of title a ruler (monarch) took is an important matter to show the characrer of a given state. The fact that the Ritsuryo-state of Japan in eighth century was based on the Chinese constitutional system and that the monarch at that time took a special title 'Tenno' (天皇, lit. ten=heaven, no=empror) should be remarked. By means of the inscription on the iron sword which was discovered recently in Sakitama-Inariyama, an old mound, we see that a monarch of Japan in fifth and sixth century was called 'Daio' 大王. The change from 'Daio' to 'Tenno' was made after seventh century according to the international negotiation with China. Therefore it seems to be sure that the name of 'Tenno' came from Chinese term. If it is true, from which Tenno of China Japanese governor took its name? And for what did he adopt the title 'Tenno'? To answer these questions, I tried to consider the thought background of the motive in this paper. Among the past studies on Tenno, Sokichi Tsuda's paper 'Tenno-ko' is a representative one. In this paper, he told that 'Tenno' had two meanings : one is the Divine Being from a point of astrological view, the other a fictitious character's name as an emperor from a view point of superhuman being with divine power. Each meaning is mainly based on the religious concept implying a metaphorical meaning of a monarch. There is a recent opinion, by Shigeru Watanabe and Haruyuki Tono, that Japanese usage is bound to that of 'T'ien-huang' 天皇 and 'T'ien-hou' 天后 used in the reign of Kao-tuung 高宗 in T'ang. There is also Yukihisa Yamao's opinion that a title of 'Tenno' which unified separated functions of T'ien-tzu 天子 and Huang-ti, 皇帝 was newly created in the reign of Tenji, but I cannot follow him. I make much of the siginificance of the establishment of 'Tenno' as a title of a monarch, but I cannot follow the view that a title of 'T'ien-huang' in the reign of Kao-tsung brought forth its adoption in Japan directly. Because T'ien-huang in the reign of Kao-tsung did not mean to strengthen the right of the monarch at all, but, on the contrary, to rationalize the direct imperial rule of Tse-t'ien-wu-hou 則天武后. And it may be said that a title of a monarch which was based on Huang 皇 as well as Tenno did not exist at all in China befofe T'ang. For example, T'ai-shang-huang 太上皇 was a dignified title for the monarch after his abdication or demise. In An-p'ing-hsien-wang Fu ch'uan 安平獻王誤孚伝 (Chin shu 晋書) 'T'ien-huang, T'ien-huang-chih-hou' 天皇・天皇之后 was used with a meaning of a dignified title for the past monarch. So I suppose that 'Tenno' at first had no clear meaning of a title of a monarch when the name came into Japan. Therefore I do not think the oldest date when the name was imported to Japan is bound to the first year of the Shang-yuan 上元 (674 A.D.) in the reign of Kao-tsung. In Suiko period when the first direct connection with Chinese title of a monach was made, the monarch called himself 'Tenshi (T'ien-tzu)' 天子 contrasting with a title 'Huang-ti' 皇帝 of China. This shows that Japanese side at that time accurately understood the title of a monarch of China. Taking these facts into consideration, I infer as follows : Till the end of seventh century a present ruler was called 'Tenshi 天子 '(Kotei 皇帝) as well as 'Daio' which was still used among the nation, and the past monarchs were called 'Tenno'. The name of 'Tenshi' means a very name of Chinese monarch, and at the same time, among the nations of Northeast Asia including the Japanese, the name means Ame-tarashi-hiko 阿毎多利思比弧 (Sui-shu 隋書), a noble man from the Heaven. While 'Tenno' in contrast with 'Tenshi', must be

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