The decision was made on Friday at a meeting of the defence ministry's procurement committee.
The SM-2 missiles were developed to provide air and cruise missile defence as part of the Aegis combat system.
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In addition, the committee also approved the granting of the Hanhwa Corporation (Hanwha) the right to manufacture 230-millimetre calibre missiles for multiple-launch rocket systems.
3 December 2018, 03:52 GMT
The South Korean defence purchase comes amid a general improvement of relations with Pyongyang, with North Korea destroying 10 observation posts in the demilitarised zone bordering the South.
There are no reports pertaining to the next inter-Korean summit; however, South Korean Foreign Minister Kang Kyung-wha and President of the Presidium of the North Korean Supreme People's Assembly Kim Yong-nam held a meeting in Mexico last week.
