Atomic force microscope (AFM) has advantages in the measurement of mechanical properties of soft materials. Here, we introduced applications of AFM to elucidate a single cell mechanics and multi-cellular dynamics. Comparison of elasticity map of fibroblasts with distribution of intracellular cytoskeletal fibers showed correspondence of high elasticity regions andactin fiber distributions. A representative morphology of cellular membrane ruffling was clearly observed and elasticity of the ruffling regions was higher than that of the outside of the ruffling regions. Elasticity map of epithelial cells showed cell-cell contact point is high elasticity. Cellular elasticity measurements by AFM will be applied to medical usages and some modifications of AFM will open a new door to study dynamics of soft materials.