Even Faxian(法顯)'s Gaosengfaxianchuan (『高僧法顯傳』) and Iching(義淨)'s Nanhaijiguineifachuan (『南海寄歸內法傳』) are regarded as very important and useful documents to study the southeast asian buddhist culture, it is very difficult to grasp the contemporary state of those area because their descriptions are very brief and implicit. Therefore this essay aimed an in-depth reading their documents as original texts of modern understanding of those area, and tried to make a new views to approach the southeast asian buddhist culture by some more historically and concretely. At the early 5th century when Faxian(法顯) arrived, Buddhism was flourished in Sri Lanka. Because already a long time passed since the Saṇgha was schismatized into conservative and progressive at around the dominical year, he mentioned nothing about the conflict or disharmony of two orders. And the faith of Buddha tooth relic, which had been uprisen at 50 years ago from Faxian's visiting, was concretely established as a representative religion of Sri Lanka. According to his record, the carrying ritual of this Buddha tooth was performed very magnificently as similar with recent Korean Youngsan ceremony(靈山齋). In the mean time, it looks there were many sculptures of Buddha image made of precious stone of special product from Sri Lanka. The faith of Buddha-pāda(the Buddha's foot-prints) was also generalized at that time. The most famous monk of his contemporary Sir Lanka was Buddhaghosa, the author of Visuddhi-magga, but it is not sure that Faxian had met him. It can be suspected that the funeral in which Faxian participated could be belonged to him, or the Visuddhi-magga was writing at the peak during Faxian's staying. On the way to return to China, Faxian embarked an indigenous ship around Indonesia. It means there were no chinese trade ship which he can use. So the trade between china and southeast asia was advanced by south asian ships, and the chinese ships were not yet joined at that time so activity. And at least until that time, it looks there were no any remarkable buddhist movement in the southeast asian countries by where he stopped. In contrast, the southeast asian world which be seen by Iching had already experienced a lot of changes. He was impressed by the high quality buddhist culture of those area, and insisted to accept it to china. Further, he analyzed the sects of buddhism which were prevalent around the southeast asia in his contemporary time, and tried to make a good relationship with each native monks for learning from them. It looks the center of those exchanges may be Śrīvijaya of Indonesia. He also mentioned the situation of the late 7th century's Funan(扶南) in Cambodia. At that time, the buddhist Saṇgha was oppressed by newly rising Khmer(眞臘). On the other hand, he described the points of sameness and difference in detail between Indian and southeast asian buddhist culture in the field of ritual as like the practical use of garments, buddha images, and daily recited scriptures. There must be a lot of another aspects which this essay couldn't gather up or catch from these documents. Nevertheless, I hope this essay can help the researchers of this field and will wait for any advices and comments from them.