Disclosed herein is a methacrylic copolymer which is a polymer of a monomer mixture comprising about 20 to about 99.9% by weight of a C6-20 aromatic methacrylate, an aliphatic methacrylate, or a combination thereof, and about 0.1 to about 80% by weight of a mono-functional unsaturated monomer. The methacrylic copolymer can have a high refractive index of about 1.495 to about 1.59, and thus when it is blended with polycarbonate resin, it is possible to obtain a methacrylic resin composition having improved compatibility without any other compatibilizer.