The latest fatality, who had lung cancer, died while undergoing treatment at a hospital in Seoul, Yonhap news agency said, citing the health ministry.
South Korea has confirmed 186 Middle East Respiratory Syndrome infections while more than 560 people remain in quarantine after possible exposure to the potentially deadly virus.
A total of 125 of those diagnosed with the virus have recovered and been released from hospital.
The outbreak started on May 20 when a 68-year-old man was diagnosed after returning from a trip to Saudi Arabia.
South Korea's government is facing criticism for failing to stop the outbreak.