Any foreign visitors wishing to enter the Republic of Korea must have a valid passport and obtain a Korean visa before coming. However, people of 99 countries who want to visit Korea temporarily are permitted to enter without a visa according to visa-exemption agreements, or in accordance with principles reciprocity of national interest.
Please check out here.
Countries under Visa Waiver Agreements
Maximum period of stay
Diplomatic, Official passport
Ordinary, Diplomatic, Official passport
Ordinary:90 days, Diplomatic·Official passport:90 days, Staff stationed in Korea : During a period of incumbency