The rolling friction of a sphere over a rigid plane is studied by finite element method, where the material behaviour of the sphere is assumed to be viscoelastic, described by the Kelvin-Voigt model. The effects of contact load, radius and rotation speed of the sphere, as well as material properties such as Young's modulus, Poisson's ratio and viscosity coefficients, on rolling friction are analysed. The results support a theoretical model formulated based on the principles of contact mechanics. (C) 2010 Elsevier B.V. All rights reserved.