Overall World Cup leader Peter Prevc was fourth, behind Kenneth Gangnes of Norway and Japanese veteran Noriaki Kasai.
The sixth World Cup victory in his career comes almost exactly three years after his last – which was likewise in Vikersund. Kranjec bagged all six victories in giant hills.
The win, with jumps of 236 and 239.5 metres, propels Kranjec among the favourites for the two weekend event in Vikersund.
"I just want to enjoy it and do my best," Kranjec said about the prospects for tomorrow and Sunday.
Peter Prevc was considered the top favourite after a spectacular trial jump. He was third after the first series with 226.5 metres, but fell short in the second, jumping only 220 metres.
Nevertheless, he extended his overall World Cup lead against Severin Freund of Germany, who finished in tenth place today. He now has 467 points on Freund.