Precedents are data containing various types of information. In this study, I proposed a method to be utilized as legal information system for the public using automatic text analysis performed on precedents. It is carried out to analyze the defamation precedent using reference provision, judgment issues, major points of judgment, and reference precedents. As a result of the analysis, legal provisions used in defamation, key issues covered by defamation, and key cases are extracted. Although only applied to the Supreme Court case regarding defamation, the proposed methodology could be applied to various legal topics.