Recently, a prosthetic hand is now popular to most amputee patients. There have been many researches to develop various mechanism. However, in contrast to the various mechanism, skin structure have been only considered for a cosmetic role. However, in the case of human hands, the mechanical properties of human skin is thought to contribute to the overall hand function. From this perspective, we developed three-layered skin pad structure which can improve the functionality of prosthetic hands. The properties of human skin was measured based on the skin pad model that has outer skin layer/subcutaneous fat layer/muscle layer. As a result, the non-linear stiffness characteristics of human skin pad was figured out. Based on this result, we suggested the three-layer skin structure, and verified its advantages on the functionality of prosthetic hands by finite element simulation and experiment. To evaluate the functionality, the stability and manipulability indexes was suggested through observing the responses against the external wrench while the object was grasped through the skin structure. Comparing with the conventional skin structure (single-layer) in various conditions, we verified that the suggested bio-mimetic three-layer skin pad structure could improve the stability and manipulability. Also, we verified that the stiffness change of conventional skin structure could not achieve these functionality.