In 1994, 115.4 boys were born in the country for every 100 girls, but the ratio has dropped to 105.6, around a natural level, it said.
However, women in the country still face more domestic responsibilities, a glass ceiling at workplaces and new forms of gender-based violence including online sexual abuse, the report said.
Crimes involving dating violence and spy cams have led thousands of women in South Korea to protest in recent years, calling for stricter penalties and enforcement of laws.
“A strong civil society and women’s groups are critical to addressing the emerging forms of violence,” Won said.
Other countries with a low birth rate included Bosnia and Herzegovina and Singapore at 1.2, and Cyprus, Greece, Italy and Portugal at 1.3.
(Reporting by Hyonhee Shin; editing by Richard Pullin)