All visitors to the Republic of Korea must have a valid passport and visa. Visitors with roundtrip tickets from countries who have a special agreement with Korea may be exempt from the visa requirement, and can stay in Korea visa-free for periods up to 30 days, or 90 days, depending on the type of agreement between two countries. When uncertain as to the requirement for entry visa to Korea , please contact the Korean embassy or a consulate as early as possible. If you are in need of an individual invitation, please contact to the secretariat(iwec@geni-pco.com). However, this invitation implies no obligation for visa. For more information, please visit the website of Korean Ministry of Foreign Affairs and Trade.
(http://www.mofat.go.kr/english/visa/apply/index.jsp)