PURPOSE: To provide antibody to polypeptide having antigenicity of B type hepatitis virus e-antigen and provide a production method.

CONSTITUTION: An antigen is produced by producing an extract of bacterial host characterized by development of polypeptides having antigenicity of Btype hepatitis virus nucleus antigen and digesting the extract by a reducing agent resistant protease in the presence of a reducing agent. Or, the antigen is produced by producing an extract of bacterial host characterized by development of polypeptides having antigenicity of B-type hepatitis virus nucleus antigen and treating the extract by a reducing agent in dissociating condition; and the extract consists of about 60% of B-type hepatitis virus nucleus antigen. Detection of an antibody to the Btype hepatitis virus e-antigen characterized by polypeptides having antigenicity of B-type hepatitis virus e-antigen and produced in such a manner is carried out. In this way, the antibody to the polypeptides is obtained, B-type hepatitis virus e-antigen characterized by the antibody is detected, and diagnosis and detection of the B-type hepatitis virus are carried out.