In order to maintain nuclear nonproliferation regime based on the Treaty on the Non-Proliferation of Nuclear Weapons, it is indispensable for non-nuclear weapon states that have acceded to implement the treaty in good faith. From this perspective, the purpose of this study is to discover ways to lead successful denuclearization of countries that have engaged in nuclear weapons-related activities. After investigating the history and analyzing the characteristics of denuclearization of eight countries, which have already achieved or whose denuclearization are currently pursued, namely South Africa, Iraq, Libya, Ukraine, Kazakhstan, Belarus, the Democratic People's Republic of Korea, and Iran, we then derived eight denuclearization factors, which are essential to consider for leading successful denuclearization. Such factors are: (a) Motivation for nuclear development (motivation for maintaining inherited nuclear weapons in the cases of Ukraine, Kazakhstan and Belarus’s denuclearization), (b) Progress of nuclear development, (c) Domestic and international circumstances at the time of denuclearization, (d) Incentives for denuclearization, (e) Effect of sanctions, (f) An international framework for denuclearization, (g) Denuclearization methods, and (h) Verification methods and a verifier of denuclearization. Finally, we concluded the relationship and combination of the above eight factors for successful denuclearization as follows: First, in order to encourage a country’s decision for denuclearization, it is necessary to provide it with any incentives for its denuclearization, such as security assurance, especially from nuclear weapon states, and sanction relief and financial support, while considering the domestic and international circumstances surrounding them. Second, upon a nation’s decision for denuclearization, under an international consensus framework involving nuclear-weapon states, irreversible denuclearization methods should be promptly implemented in accordance with its progress of nuclear development. Simultaneously, in a parallel with denuclearization, and except for nuclear weapons verification that should be completed by nuclear weapon experts in nuclear weapon states, the International Atomic Energy Agency verifies and monitors its denuclearization, principally based on verification methods which have already been implemented under the Comprehensive Safeguards Agreement and Additional Protocol.