The German’s seventh win of the season, ahead of his Red Bull Racing teammate Mark Webber, and Jenson Button’s McLaren-Mercedes, leaves him 92 points ahead with seven races left of the championship.
The race at Spa-Francorchamps was full of overtaking as the teams struggled with tyre degradation after having little dry running in practice due to wet weather.
Vettel was passed on the opening lap by Nico Rosberg’s Mercedes GP, but retook the lead easily on lap three.
He dropped back down to eighth after an early pit stop, but regained the lead when Fernando Alonso pitted in his Ferrari.
Lewis Hamilton’s dreams of a second successive win in Belgium were shattered when he crashed out on lap 13 after colliding with Kamui Kobayashi’s Sauber as he looked to complete an overtaking move at Les Combes.
This brought out the safety car and Vettel dropped to third after pitting. He passed Webber and Alonso immediately after the restart and even though he had to do the last stint of the race on hard tyres, he cruised home to triumph.
Webber and Button both charged through the field after making early pit stops, and both passed Alonso, who had to settle for fourth, in the final 10 laps.
The Mercedes pair of Michael Schumacher and Nico Rosberg completed the top six.