The problem to be solved is to provide an anti-human MUC1 antibody Fab fragment that is expected to be useful in the diagnosis and/or treatment of a cancer, particularly, the diagnosis and/or treatment of breast cancer or bladder cancer, and a diagnosis approach and/or a treatment approach using a conjugate comprising the Fab fragment. The solution is an anti-human MUC1 antibody Fab fragment comprising a heavy chain fragment comprising a heavy chain variable region consisting of the amino acid sequence represented by SEQ ID NO: 8 or 10, and a light chain comprising a light chain variable region consisting of the amino acid sequence represented by SEQ ID NO: 12, and a conjugate comprising the Fab fragment.
