The present invention relates to an antibody or an antibody fragment thereof which recognizes an extracellular domain of erbB3 and inhibit EGF-like ligand-dependent phosphorylation of erbB3, a DNA encoding the antibody or the antibody fragment thereof, a method of producing the antibody or the antibody fragment thereof, a therapeutic drug including the antibody or the antibody fragment thereof, and therapeutic application using the antibody or the antibody fragment thereof.
