An ethylene-based copolymer for non-crosslinked water supply pipe is provided. The ethylene-based copolymer is prepared using a supported hybrid metallocene catalyst and has a dimodal or broad molecular weight distribution. The ethylene-based copolymer has a high density molecular structure in a low molecular weight and has a low density molecular structure with high content of a comonomer in a high molecular weight. The ethylene-based copolymer has a molecular weight distribution of 5-30 and the distribution of copolymerization of ethylene and C.sub.3-20 .alpha.-olefin is localized in high molecular weight chains. Accordingly, the ethylene-based copolymer has superior processability, internal pressure creep resistance at high temperatures and environmental stress crack resistance.