Chip makers ended higher, helped by a slight rise in the Philadelphia Stock Exchange's semiconductor index and as investors bet earnings at local semiconductor firms were set to improve on rising demand for memory chips.
Samsung Electronics Co Ltd, the world's biggest maker of memory chips, ended up 0.19 percent to 520,000 won, while Hynix Semiconductor Inc rose 3 percent to 15,500 won after earlier hitting a 12-month high of 16,350 won.
Kookmin Bank, South Korea's top lender, fell 1.42 percent to 45,150 won.
Trade volume reached 557 million shares worth 3.4 trillion won compared to 548 million shares worth 3.4 trillion won on Tuesday. Gainers edged out losers by 380 to 371 with 62 titles ending flat.
Foreign investors bought a net of 123 billion won ($120.1 million) in shares on the main bourse, while retail investors sold a net of 12.2 billion won. Institutional investors sold a net of 143.9 billion won.
The March KOSPI 200 futures index rose 0.85 point to 126.10 and the underlying KOSPI 200 spot index added 0.37 point to 125.85.
The over-the-counter Kosdaq rose 1.02 percent to finish at 513.25, its sixth consecutive gaining session and its highest close since ending at 522.2 on July 16, 2003.