Pretty much says it all. They take a hypothesis (myth), they perform experiments to test it (the fun part), and then they publish their conclusions for everyone to see (the show). If "form hypothesis - conduct experiment - publish results" isn't science, then I don't know what is.
Mind you, MythBusters isn't always good science. It's not usually rigorous science. But it IS science, any way you cut it. (It's also often engineering, and almost always entertainment. Hardly a bad combination.)