Finite element analysis of CMP process was studied to understand uneven pressure distribution between polishing pad and wafer. Since WIWNU (Within wafer non-uniformity) is mainly influenced by dynamic viscoelastic properties of CMP polishing pad, the dynamic property of the polishing pad has to be understood first for dynamic finite element analysis of the process. To measure viscoelasticity of the polishing pad, time-dependent strain data by load were obtained using a viscoelasticity measurement system capable of measuring deformation by periodic load. Primary and secondary elastic modulus and relaxation time could be achieved for the behavior of the polishing pad by load. Finite element analysis was carried out under the same conditions as viscoelastic measurement. Material properties of the polishing pad were assumed based on results of experiments. By comparing experimental results with analytical results, material properties in the analytical model were modified and FEA was carried out again. It was confirmed that the behavior of the polishing pad by load in the experiment and FEA according to modified material properties were well matched. Through this process, viscoelastic properties of polishing pad were well defined for dynamic analysis of CMP process.