The German made it look easy despite hitting a speed of 71km/h as he hit the line leaving Demare and Andre Greipel (Lotto Soudal) to fight for the podium scraps on the right hand barrier. Australia's Michael Matthews (Team Sunweb) had to settle for seventh.
Kittel took advantage of a strong lead out from his blue train which organised itself several kilometres out from the line.
"First of all, I want to say that I'm very proud of my team," Kittel said. "They did a great job. It was very different from Liege. They managed to position me well and keep me there. It was important for the victory.
"I had a good wheel. I saw Demare go first and I had to go at the 150 metres. It worked perfectly. I was a little bit behind when my opponents went. I feel good at the moment.
"The green jersey is within reach but the more important is the victories because they also give you a big advantage for the green jersey. I will also try to get points in the intermediate sprints and we'll see in one and a half weeks."
Demare thought he just had Greipel to contend with, but he sure was wrong.
"Yes I believed in my chances when I was starting to overtake Greipel," the Frenchman said.
"And then I saw a blue wing fly past me on the left."
"From where I was trying to go on the right, it was really on the edge. I was not 100 pc in my sprint, more in my line. I have no regrets. I keep scoring points for the green jersey and that's reassuring. There is a big battle with Kittel.
"He has two wins but in the intermediate sprint, I played it well. The Tour is very long and we cannot say it's in the bag. Tomorrow, we're at it again"
Eagle-eye view of the final sprint
As it happened
Perrig Quemeneur (Direct Energie), Frederik Backaert (Wanty) and Vegard Stake Laengen (UAE) pulled clear from the start. Their lead hit a maximum of four minutes after 30 kilometres raced, and hovered around two minutes with a few incursions to back over the three-minute mark.
Backaert and Laengen left Quemeneur to the KOM point on both category four climbs, while they battled for the points at the intermediate sprint in Colombey-les-Deux-Eglises.
The Belgian rider Backaert took maximum points. Back in the bunch, now just over a minute behind, Colbrelli tried something with an early lead-out before the line, but Demare was just too strong, edging out Matthews. Here too, Kittel scooped up six points, the virtual top three looking something like this: Demare: 140 points, Kittel 93, Matthews: 84 points.
After the stage, Demare now sits on 170 points, enjoying a 27 point lead over Kittel.