The graft density of poly[poly(ethylene glycol) methacrylate] (PPEGMA) was controlled using atom transfer radical polymerization to observe the change in the differentiation behavior of stem cells because the alteration in the graft density leads to the altered surface elasticity However, since the cells do not adhere on the high graft density polymer brush, it is impossible to observe such behavior directly We therefore immobilized collagen onto polymer brushs with controlled graft density to obtain a surface which is effective for cell adhesion and maintains its different surface matrix elasticity For the cell adhesion, the human mesenchymal stem cell (hMSC) adhesion and differentiation was investigated on the surface of collagen-immobilized polymer brush It was shown that the hMSC spreading tendency was altered by the surface elasticity implying that the behavior of hMSC would be altered by the stiffness of the polymer brush