Okay, it's a funny title, but many pet owners want to know!
Flatulence (the polite term for "fart"), as well as burping, is usually caused when your dog swallows too much air when eating quickly. The same thing happens with humans.
Your dog's diet could also be contributing to his excessive farting. Foods that contain soy, and other foods that are highly fermentable, as well as uncooked greens, can all cause excessive flatulence in your dog.
To help reduce the farting problem, try feeding your dog several small meals of low-fiber food that is easy to digest. There are also some over-the-counter products, such as activated charcoal and simethicone (OTC strength), that help absorb excess intestinal gas.
If your dog doesn't appear to be in pain, then his flatulence problem is probably more of a concern for you than it is for him!