You can, but definitely shouldn't.

Dogs have skin that is much different that ours--not just in obvious ways, like the lack of sweat glands, but more notably in the pH levels. Dogs have a higher skin pH than we do. Human shampoo, which has a higher acidity, messes with the balance of a pup's skin. It has a likelihood of drying the skin out a bit, which means stripping natural oils away, which means stripping a pooch's natural defense barrier against disease and infection away.

Do the respectful thing and spend a few dollars more to get a shampoo specifically designed for your best friend. You will sleep better--and so will he. :)