JB Financial Group posted the only earnings increase among provincial banks, up 4.3 percent from last year to 96.5 billion won.
BNK and DGB financial groups, the other South Korean provincial banks, both suffered net income dip blamed on COVID-19.
Busan-based BNK maintained the top spot, but its net income dropped 22 percent to 137.7 billion won.
The North Jeolla Province-based JB Financial Group came in second, dislodging DGB from the spot.
Daegu-based DGB earned 88.2 billion won, down 15 percent year-on-year. The dip was due to a decrease in net interest margin and an interest rate cut.
JB's net income increase is attributed to the excellent performance by JB Woori Capital, its credit loan unit, which exhibited a net income boost by 32.1 percent to 25.8 billion won.
Its benchmark Jeonbuk and Kwangju banks displayed 13.8 percent and 3.1 percent net income increases from last year, with 29.6 billion won and 46.7 billion won, respectively.
Meanwhile, DGB's benchmark Daegu Bank earned 78.7 billion won in net income, which was a 10.4 percent decrease from last year. The group's non-banking subsidiaries, DGB Capital, DGB Life Insurance, and HI Investment & Securities, posted earnings of 7.6 billion won, 9.2 billion won, and 13.1 billion won.
BNK's benchmark Kyongnam and Busan banks posted net incomes of 47.4 billion won and 87.4 billion won, respectively, down 24.2 percent and 22.7 percent.
The group's BNK Saving Bank exhibited earnings of 4.2 billion won, a 26.3 percent dip from a year earlier, while BNK Securities' net income plummeted 2.9 percent to 6.8 billion won.
The outcome was attributed to the extensive spread of the coronavirus in the southeastern region in February and March.