In the development of Taiwanese folktales, Japanese rule period is an important stage. The collected Taiwanese folklores written in Japanese in this period even occupied a leading role during the developing process. Based on the situation in above, this paper will discuss the importance of the collected Taiwanese folktales written in Japanese in this period and will focus on the range of the folktales by the Hang ethnic group. After classifying the works, we can see that there are three points. First is the essential role of the folktales in the development. The collected Taiwanese folklores published in Japanese in this period is helpful to offer a lot precious clues to figure out how the folktales in contemporary Taiwan sustain in current styles. Second is that these collective works are abundant and various in kind. The stories in these collected works are full with Taiwanese color, relate to Chinese classics and even adopt the plots from the world literary works. Because of the abundant contents of the stories, the Taiwanese folktales are able to incessantly develop and become flourish today. Third is making up the lack and promoting the vales of folktales. The study of the collected Taiwanese folktales published in Japanese in Japanese rule period need to be broadened. If lack of this study could be made up, it would be helpful to make the developing processes clear. Moreover, through connecting with the other international studies and helping the researches of Taiwanese folk cultures will be able to promote the academic values of Taiwanese folktale study. In current, due to lack of the research on Taiwanese folktales written in Japanese under Japanese rule period, the study of this field in colonial Taiwan under Japanese rule is definitely important. I hope this paper will play a pioneer role to urge people to pay attention on this field, then to study on the compiling process of these collected works and to analyze them and to study the various in meanings.