The Quick Step rider easily won a bunch sprint ahead of German rival Erik Zabel of the Milram team with South African Robert Hunter, winner of Thursday's stage, coming home third for the Barloworld team.
Boonen, who won the sixth stage in Bourg-en-Bresse, now leads Hunter by 20 points in the sprinters' standings.
“Yesterday, I was not lucky, today was okay,” said Boonen, who missed Thursday's sprint after being delayed by a big crash in the final kilometre.
“I had won the last sprint before the Alps, now I win the last sprint before the Pyrenees. It's good for my morale.”
Dane Michael Rasmussen finished safe in the peloton to retain the overall leader's yellow jersey.
The Rabobank rider is at the centre of a controversy after the Danish Cycling Union announced it had dropped him from the national team after he received several warnings from the International Cycling Union and anti-doping authorities.
Rasmussen failed to inform the authorities of his whereabouts while training and therefore missed two random dope tests in May and June.