The 28-year-old's success sent him top of the slalom standings with 195 points after three races.
Switzerland's slalom world champion Loic Meillard was second, after winning a giant slalom on Saturday and going fastest in the opening leg by 0.05, with Norway's Henrik Kristoffersen third for his 97th podium.
Norwegians filled four of the top six places, with Oscar Andreas Sandvik fifth and Hans Grahl-Madsen sixth.
"I was very nervous... so many guys going out, doing a lot of mistakes," said Haugan after his sixth career win.
"It could happen to me as well, but I managed to follow my plan and avoid big mistakes."
The Norwegian, second after the first run, had questioned earlier in the morning whether he would be able to race due to some back pain, but was happy he did.
"It was pretty bad this morning, but then it actually got a little bit better," he told TNT Sport.
Meillard was last to run and crossed the line 0.28 seconds slower than Haugan's combined time of one minute 37.89 seconds.
Italy's Alex Vinatzer set the fastest time of 49.21 in the second leg to finish fourth after being 25th in the opening run down the Face de Bellevarde slope.
Olympic champion Clement Noel of France was one of five who failed to finish the second leg.
Norway's Atle Lie McGrath and Brazil's Lucas Pinheiro Braathen, third and fifth respectively after the first run, both straddled gates on their second attempts.
The next men's slalom is in Italy's Alta Badia resort on December 22nd. There have been three different winners in the discipline so far.