The present invention relates to an antibody conjugating peptide including an amino acid having a photoreactive functional group, a physiologically active substance modified with the conjugating peptide, and an antibody conjugate having an antibody linked to the physiologically active substance. When the physiologically active substance modified with the conjugating peptide according to the present invention is linked to the antibody, the conjugation efficiency between the antibody and the physiologically active substance is remarkably improved as compared to that of the conventional art, and thus, the drug may be firmly bound without impairing the specificity of the antibody, thereby making it possible to accelerate commercialization of the antibody conjugate.