Surface morphology of Nafion 117 membrane was studied by tapping mode atomic force microscopy. Three different samples were analyzed and correspond respectively to dry membrane and wet membrane equilibrated either with water or with tributylphosphate. These studies show the supermolecular structure of the membrane, which is made of nodules or spherical grains of a mean diameter of 11 nm, and are surrounded by interstitial regions of a mean thickness of 50 Angstrom. Roughness analysis of the samples shows the influence of the swelling properties of the membrane on its surface morphology.