Like pastery baking, potion making seems to be a form of chemistry. The difference being that the average muggle doesn't have the components avialible to them that a wizard does. And from what it seem like in the books, the wizarding world makes damn sure that those things, like pheonix feathers, wizard mandrake, and anything else that appears animate never falls into muggle hands.

I don't see any reason why a muggle *couldn't* make a potion if they had the right stuff.