As for the question when “Courtroom Drama” was formed, some books on history of literature at my hand mention that it has been developed based on Can-Jun-Drama during the Northern Sung period. Tracing to its source, such a viewpoint seems to follow the descriptions which are often seen in “Study of Yuan Ren Courtroom Drama” written by Masaru Aoki. Although a leading figure in Dramas living in the same period, Wang Guowei, didn’t pursue this issue deeply, he also seems to regard the origin of “Courtroom Drama” as around the Northern Sung period. Afterwards, Ren Bantang insisted that sort of Dramas or plays were already formed in the Tang Dynasty, but his opinion has neither been widely accepted, nor attracted future generations. In fact, ensuring historical verisimilitude of a large literature carefully in the Tang and Northern Sung Dynasty, I’ve found that performance style of “Courtroom Drama” was already established in the Tang Dynasty, along with Can-Jun-Drama and Puppetry. In addition, “Courtroom Drama” spread not only at the inner courts in Chang An and Luo Yang but also in the Jiedushi’s governments (Jiedushi is regional military governor in ancient China) and temples spotted in local areas. This thesis provides evidence to prove that “Courtroom Drama” existed already in the Tang Dynasty and also analyzes about performance styles of “Courtroom Drama” based on historical records.