The primary investigation is the beginning of the public prosecutor's contact with the case through investigation. Only the Public Prosecution, which is authorized by law to investigate the various crimes, including the offenses of Listed Companies Data In the stock market. The primary investigation of these crimes is of a special nature. It requires that the members charged with the investigation be sufficiently knowledgeable and knowledgeable about the techniques of this type of crime so that they can complete the investigation in a manner that reveals the facts in full. The aim of this study is to clarify the importance of the preliminary investigation into the crimes of Listed Companies Data In the stock market and to clarify who is conducting this investigation in order to reach the ultimate objective of achieving justice and achieving criminal protection of Listed Companies Data In the stock market. During our study, we faced many problems, the most important of which is: What is the direct way of investigating him? And how to conduct the investigation after completion? How is the problem of determining the competent authority to investigate this type of crime resolved?