The Bank of Korea's manufacturing business survey index (BSI) for December stood at 83 on a seasonally adjusted basis, inching down from 84 in November.
A reading below 100 means that there were more panelists who were pessimistic about future business conditions than were optimistic. The last time the index topped 100 was in September 2010.
The December sub-index for mid-to-small-sized businesses stood at 70 in January, down 2 points from 72 the previous month, the BOK survey showed.
Manufacturers who categorize themselves as exporters also slumped 2 index points to 89 , as export growth showed some signs of slowdown during the fourth quarter.
South Korea's export growth slowed but still recorded 13 straight months of expansion in November. Trade data for December is due on Jan. 1.