He graduated from Gyeonggi High School and the Department of International Relations at Seoul National University.

In 1979, he began his career as a diplomat at the United Nations Department of Foreign Affairs and North American Affairs Bureau. Since 1991, he has formed a long-standing relationship with North Korea, by serving as an attaché of the inter-Korean nuclear negotiation for the Blue House and the Embassy of South Korea at Washington, D.C., the Representative of the North Korean Light-water Reactor Negotiation, the Manager of North American Affairs Bureau1, the Director-General for the Blue House National Security Council (NSC) Policy Coordination Bureau, the Director-General for Policy of KEDO Bureau, the Director-General for North Korean Nuclear Negotiation Planning, Ministry of Foreign Affairs, the Deputy Chief of the Six-Party Talks, the Ambassador to the North Korean Nuclear Issue, and the Deputy Minister of Foreign Affairs.

He has published Vietnam, Scars of Forgotten War(2003, 2014 revised edition), North Korean Nuclear Weapon, New Game Rule(Seoul, 2005, Tokyo), and The End of the Game: The Truth and Illusion behind 20 years of North Korean Nuclear Negotiations, and Everything Thereafter(2010 Seoul, 2015 Tokyo).