Various human monoclonal antibodies that bind to human TGF-.beta. type II receptor to inhibit the signal transduction of human TGF-.beta. signal into cells are produced by immunizing human antibody-producing transgenic mice generated by genetic engineering techniques with the soluble human TGF-.beta. type II receptor. Further, these human monoclonal antibodies were demonstrated to be effective for preventing and treating various diseases induced by human TGF-.beta. in various organs (for example, tissue fibrosis).