The T-50B aircraft hit a mountain in Hoengseong shortly after taking off, the air force said. The plane is a trainer jet flown by the military's Black Eagles aerobatic team. Hoengseong is about 70 kilometers (45 miles) east of Seoul.
Military officials found a parachute near the crash site but the pilot apparently failed to escape, the air force said. Authorities found the body of the air force captain inside the cockpit.
The cause of the crash was unclear.
Another Black Eagles pilot died in 2006 when his plane crashed during an air show. In June this year, the Black Eagles team won an award for best overall flying at an air show in England.