Disclosed are an antibody which have a binding activity to human betacellulin protein or a mutein thereof with specificity; especially a monoclonal antibody which does not have cross reactitivity with human epidermal growth factor (EGF) and human transforming growth factor a (TGF-&agr;), belongs to the immunoglobulin class of IgG, and,specifically binds to human betacellulin protein to neutralize biological activity thereof; a hybridoma for producing the monoclonal antibody; and a method for producing the monoclonal antibody. Said monoclonal antibody neutralizes biological activity of a human BTC protein, and bind to the protein with high sensitivity and specificity, so that they can be used as a therapeutic agent for diseases such as arterial sclerosis and cancers, and also used as a reagent for assaying the human BTC protein or a mutein thereof and as a diagnostic agent for diabetes or complications thereof.