The benchmark Korea Composite Stock Price Index rose 0.86 point, or 0.04 percent, to 2,365.80 in the first 15 minutes of trading.
On Tuesday, North Korea lobbed a ballistic missile over Japan in a move that can sharply raise tensions in Northeast Asia.
Market kingpin Samsung Electronics was 0.39 percent up, while SK hynix, a major chipmaker, rose 1.18 percent.
Hyundai Motor, the No. 1 automaker, dropped 2.78 percent, while AmorePacific, the country's top cosmetics maker, lost 1.36 percent.
The local currency was trading at 1,124.40 won against the US dollar, up 1.6 won from the previous session's close. (Yonhap)