The relationship between labor unions and antitrust law in Korea is complex and has not been clearly defined in theory. In practice, the Fair Trade Commission (FTC) has applied antitrust law to the actions of labor unions that have been granted a certificate of establishment under the Labor Union Act. This has led to a sharp conflict, not only in terms of interpretation, but also in terms of policy. A thorough and in-depth review of the application of antitrust law to the scope of labor law is an urgent task for the labor law community. Recently, some research has been conducted on this issue, and this paper aims to review the relevant discussions in Japan as a preliminary work before conducting a full-scale review of the application of antitrust law to labor unions and labor unions. In Japan, since 2010, the Supreme Court of Japan has interpreted the term “worker” under the Labor Standards Act more broadly than the term “worker” under the Labor Union Act. This has led to the need to clarify the relationship between labor law and antitrust law in cases where a labor union or labor union under the Labor Union Act can be evaluated as a business operator or business association under the Antimonopoly Act. Recently, there have been active discussions on the deadlock between labor law and antitrust law. The discussions in Japan on the relationship between labor law and antitrust law give us the following insights. First, it is necessary to study the legislative history of the Fair Trade Act of Korea. Second, it is necessary to deepen interdisciplinary research between labor law and antitrust law. Third, it is necessary to carefully review the possibility of applying antitrust law to the scope of labor law. Fourth, it is necessary to clarify the protected area of the three labor rights.