Gross domestic product grew 0.7% from the previous quarter, down from the
1.6% expansion seen at the end of 2007.
Falling exports were largely to blame for the quarterly slowdown along with
weak consumer spending.
President Lee Myung-bak took office in February promising to boost annual
growth to 7% - it grew 5% in 2007.
The investment bank Goldman Sachs said it was keeping its growth forecast for
the full year at 4.8% despite the weak quarterly figures.
It predicted the government's programme of tax-cuts and deregulation would
boost growth while the weak currency would help exporters.
Inflation figures were also released on Friday, with consumer prices rising
3.9% in the year to the end of March.
That figure is above the government's target of between 2.5% and 3.5% for the
fourth month running.