With the use of macromonomers that have a dicarboxyl group, polycarbonate-poly(methyl methacrylate) (PC-PMMA) graft copolymers were prepared, and the relationship between the length of PMMA branches and Vickers hardness of the graft copolymer was investigated. With the use of the PC-PMMA graft copolymer as a modifier to improve the surface hardness of PC, Vickers hardness of PC/PC-PMMA blend polymers was examined. PC/PC-PMMA blend polymers are more transparent than PC/PMMA blend polymers. PC/PC-PMMA blend polymers are superior in Vickers hardness to PC/PMMA blend polymers, although the content of PMMA in PC/PC-PMMA blend polymers is smaller than that of PC/PMMA blend polymers.