Operating profit was 1.34 trillion won ($1.16 billion) during the January-March period, down 15.5 percent from the same period last year.
The profit declined 11.4 percent, from the previous three-month period, Xinhua news agency reported.
Net income slumped 10.8 percent from a year earlier to 1.77 trillion won in the first quarter, but revenue increased 6.7 percent to 22.35 trillion won.
