<p>　Late doctor Masao Shimada improved the research field of legal history regarding Northern Asia. Mongolian legal history is the most prosperous theme in the field about which large amount of research has been published in western countries, Japan, Mongolia and China (especially Inner Mongolia) recently. In this paper, we introduce and criticize the main research regarding Mongolian legal history, divided into five chapters : overall history, the period of the Mongolian Empire, the Northern Yuan period, the period under the Qing dynasty and the period after 1911.<br>　The Russian scholar Riasanovsky arranged different periods of Mongolian legal history into a united history for the first time. Despite this achievement his research is not regarded highly nowadays, because he had never read the legal resources written in regional languages. On the other hand, Shimada researched by himself widely the legal resources written in Chinese and achieved greater clarity regarding the Mongolian codes under the Qing rule. However, his name isn't famous in western countries, because he didn't read the resources nor research written in Manchu, Mongolian, and western languages. There was no correlation between Shimada's and western research.<br>　It has been debated recently whether the code of Great Yasa established by Chingis Khan existed as a written code or not in the period of Mongolian Empire. In the case of the Northern Yuan period, some codes written in Mongolian have been researched philologically, but only the Qalq-a jirum is researched using legal methods. In the case of the period under the Qing dynasty, research regarding the Mongolian codes and the judgment system which were begun by Russian scholars has been inherited by Japanese, Inner and Outer Mongolian and western scholars. A large amount of research has been published recently. Inner and Outer Mongolian scholars have begun to research the period after 1911, but this research remains scarce.<br>　In addition to philological research, research of a more legalistic nature about every period is necessary in future. </p>