The present invention relates to an antibody and an antibody fragment thereof that recognizes the extracellular region of erbB3 and inhibits the phosphorylation of EGF-like ligand-dependent erbB3, DNA that encodes this antibody and antibody fragment, a method for manufacturing this antibody and antibody fragment, a therapeutic drug containing this antibody and antibody fragment, and the therapeutic use of this antibody and antibody fragment.