Cheating SUUUUUCKS. That said, sometimes people are able to work through it.
I'd say if there was a problem in the relationship that was the underlying cause of the cheating then maybe that's worth exploring together before leaving for good. He also could have come to you with his problems before he decided to go out and sleep with someone else!
If there's any doubt in your mind I'd say leave. You can definitely find someone else and you deserve someone who isn't going to pull this crap. I'm so sorry this happened to you and I hope the next dude is less of an asshole <3