According to the North Korean state media, the leader visited a newly built residential district and the Natural Energy Institute of the State Academy of Sciences. It was Kim's first public appearance since September 3.
"Our scientists are patriots who are devoting all their lives to building a rich and powerful nation," he was quoted as saying.
During his absence from public, the media across the world indulged in debates on whether the ruler is sick. He had also missed a couple of key national events during the 'exile'.
Kim became North Korean leader in December 2011 after his father died of a heart attack.
In July, he appeared on a television show walking with a limp. Ever since, there have been wide spread speculations on his health. The ruler has a bad health which the ruling party did not want to reveal to protect his image, experts said.
There were also rumours that Kim had been ousted from power in a coup. North Korean diplomats in New York and Seoul condemned the speculation as an attempt to destabilise the regime, said a Guardian report.
There were also speculations that Kim Yo-jong, the 27-year-old sister of the ruler, who was appointed as a "senior official of the party central committee" in March, was doing some of her brother's responsibilities.
Yo-Jong is supposedly an active adviser to her brother in administrative affairs.