The present invention relates to a copolymer resin for ultra-shortwave light source such as KrF or ArF, process for preparation thereof, and photoresist comprising the same resin. The copolymer resin according to the present invention is easily prepared by conventional radical polymerization due to the introduction of norbonyl(meth)acrylate unit to a structure of copolymer for photoresist. The resin has high transparency at 193 nm wavelength, provides increased etching resistance and enhanced adhesive strength due to a hydrophilic functional group in the norbonyl group, and shows excellent resolution of 0.15 &mgr;m in practical experiment of patterning.