All visitors to the Republic of Korea must have a valid passport and visa.
Jeju island is a visa-free area in Korea for most foreign visitors*, when landing in Jeju international airport directly from foreign countries.
(*The visitors from Ghana, Nigeria, Sudan, Macedonia, Syria, Afghanistan, Iraq, Iran, Kosovo, Cuba, and Palestine need a valid visa even for direct flight from foreign countries.)
For visitors who want to visit other places in Korea or need to pass through other Korean airports before coming to Jeju Island, a valid visa may be required depending on your nationality. Visitors can stay in Korea for periods of up to 30 to 90 days, depending on the type of agreement between Korea and their countries.
For detailed information, please contact the local Korean consulate or embassy in your country or visit the website http://www.hikorea.go.kr