The present invention provides: an antibody exhibiting specificity for MUC1, the antibody having a glycan structure expressed at high levels in cancer cells； a method for manufacturing this antibody； and a novel means and method for the diagnosis and prevention and/or treatment of cancer using this antibody. The present invention is a monoclonal antibody to human MUC1, wherein the antibody specifically recognizes a glycopeptide having a human MUC1 tandem unit and furthermore having an O-linked glycan core (0(Tn)) in any one of the threonine and serine in the amino acid sequence of this human MUC1 tandem unit. A method for detecting MUC1 in a human body-fluid sample. A kit including this monoclonal antibody. A pharmacological composition for the prevention and/or treatment of a malignant tumor, the pharmacological composition containing this monoclonal antibody as an active ingredient.
