The present invention relates to a monoclonal antibody or antibody fragment thereof as a human IgG antibody including at least one lysine derivative in a constant region of the human IgG antibody; a modified antibody or antibody fragment thereof, wherein the lysine derivative is modified; a nucleic acid including a nucleotide sequence encoding the antibody or antibody fragment thereof; a vector including the nucleic acid; a transformed cell obtained by introducing the vector into a host cell; a method for producing the antibody or antibody fragment thereof; and a composition containing the antibody or antibody fragment thereof.