The benchmark Korea Composite Stock Price Index closed at 2,049.93 points on Friday, down from 2,091.52 points a week earlier.
The index started strong on Monday as investors were buoyed by hopes on the upcoming US-China trade talks.
The index then dropped by more than 1 percent on Wednesday, ending a run of thirteen consecutive sessions of gains, amid escalating woes over a potential impeachment inquiry into US President Donald Trump.
The KOSPI briefly rebounded on Thursday before falling by more than 1 percent on Friday, as investors worried about the bleak outlook for the global chip sector and political uncertainties in the United Sates.
"There will be persistent uncertainties over the issue of impeachment of Trump but there are also hopes for trade talks between the United States and China," Kim Byong-yeon, an analyst at NH Investment & Securities, said.
The analyst said poor earnings reports by major companies may increase market volatility next week.
Kim forecast the main stock index to trade between 2,040 and 2,100 points in the coming week. (Yonhap)