When the second U.S.–North Korea Summit in Hanoi, Vietnam ended abruptly without a deal, critics and experts argued that U.S. President Trump, considering the domestic pressure, changed his goals and interests at the very last minute. To theoretically explain the negotiation process in Hanoi, this study analyzes the win-set structure of the United States and North Korea. This study also aims to examine the causes of the failure by comparing the agreement zones between the United States and North Korea’s win-sets before and after the summit. Two-level game theory explains how negotiating countries with conflicting interests achieve an agreement and what kinds of strategies the governments use to maximize their own national interests. The key assumption of the two-level game theory is the linkage between domestic politics and international affairs, and the interconnection was widely suggested by many scholars including Gabriel A. Almond, James N. Rosenau, and Bruce M. Russett. Building on to this literature, Putnam’s two-level game theory introduced the concept of a “win-set” and examined the international negotiation process thoroughly using this theoretical model. Based on the analysis of the two parties’ win-sets, this study finds that the United States intentionally ended the negotiation without a deal by contracting the size of its win-set. The United States shifted its interest from the original position, which is “trading partial (or symbolic) dismantlement of North Korean nuclear weapons with partial removal of economic sanctions,” to the new interest position including the abandonment of Weapons of Mass Destruction (WMD) referred to as “Yongbyon Plus Alpha” and the agreement on a roadmap to denuclearization.