Vettel jumped ahead of Lewis Hamilton, who started on the pole, in the opening lap and held the lead for almost the entire 44-lap race around the 4.4-mile Spa-Francorchamps track.
Vettel, driving for Red Bull Racing-Renault, did lose the lead for a brief time when he had a pit stop on the 15th lap but still finished the race comfortably in charge.
He was 16.869 seconds ahead of Ferrari's Fernando Alonso with Hamilton, in a Mercedes, third about another 11 seconds behind. Nico Rosberg, Hamilton's teammate, was fourth and Mark Webber, Vettel's teammate, came in fifth.
It was the 31st career Formula One championship for Vettel, tying him with Nigel Mansell for fifth on the all-time win list. Alonso is fourth on the list with 32. Vettel won previously this year in Malaysian, Bahrain, Canada and Germany.
The win pushed his 2013 drivers' standings point total to 197, which is 46 points ahead of Alonso, who is second. Hamilton is third at 139 with Kimi Raikkonen, whose Lotus-Renault racer went out on the 25th lap Sunday due to a brake issue, in fourth with 134 points.
The Formula One circuit next races the Italian Grand Prix at Sept. 8 at Monza.