As the world develops, the globalization era grows rapidly, businessmen are racing to expand their businesses. Law No. 5 of 1999 regarding the Monopolistic Practices and Unfair Business Competition which further implemented by the Government Regulation No. 57 of 2010 regarding Corporate Mergers and and Share Acquisitions that Result in Monopolistic Practices and Unfair Business Competition regulate about the prohibition of practicing the unfair business competition and the supervision of merger that might cause the abuse of dominant position by businessmen. Indonesia has implemented the mandatory provisions of notification on merger at least 30 (thirty) days after it takes effect, whereas compared to Japan and South Korea, which have implemented the mandatory provisions of notification in line with the international standards, shows crucial differences. In accordance with those 2 (two) laws, in connection with the supervision of merger that has been implemented in Indonesia, the Business Competition Supervisory Commission is utilizing many assessments like Herfindahl-Hirschman Index to seek if the merger that has been done by businessmen might cause unfair business competition or abuse of dominant position. The first issue that will be discussed is to compare the mandatory notification provisions among Indonesia, Japan and South Korea. The second issue is to analyze the merger supervision that might cause the abuse of dominant position. The research method used is normative juridical. The results of the research indicate that the mandatory provision of notification implemented in Indonesia is still considered to be ineffective because it is more difficult to abort the merger that has been take effect rather than to prevent the merger through the pre-notification requirement. In addition, the supervisory arrangements for abuse of dominant position has been well implemented because they have described the details of abuse of dominant position.