The present invention relates to a novel monoclonal antibody that binds specifically to delta-like ligand (DLL4), and more particularly to a monoclonal antibody that binds specifically to human delta-like ligand 4 to effectively inhibit the interaction between delta-like ligand 4 and Notch receptor, a polynucleotide encoding the monoclonal antibody, an expression vector comprising the polynucleotide, a transformant comprising the expression vector, a method for preparing the monoclonal antibody, a pharmaceutical composition for preventing or treating cancer comprising the monoclonal antibody, a composition for diagnosing cancer comprising the monoclonal antibody, a method for diagnosing cancer using the monoclonal antibody, and a pharmaceutical composition for preventing or treating autoimmune disease comprising the monoclonal antibody.