Since joining the Ministry of Foreign Affairs in 1979, Ambassador LEE Byong-hyun has mainly focused on multilateral diplomacy. He played a key role in securing the Republic of Korea's accession to the UN (1991), its first-ever Security Council membership (1996-1997 term), and its participation in UN Peacekeeping Operations (UNPKO).

Ambassador LEE's distinguished career includes ambassadorship to Norway (2010-2013) and service as Ambassador and Permanent Delegate to UNESCO (2015-2019). As Ambassador and Permanent Delegate to UNESCO (2015-2019), he significantly contributed to UNESCO activities, serving as Chairman of the Executive Board (2017-2019 term) and successfully chairing the twelfth session of the Intergovernmental Committee for the Safeguarding of the Intangible Cultural Heritage (December 2017, Jeju Island, Korea).