It is intended to find a highly specific epithelial ovarian cancer marker and to provide an antibody capable of specifically recognizing and detecting the marker or a fragment of the antibody. The present invention provides an anti-β1,6-N-acetylglucosaminyltransferase 5B antibody for diagnosis of epithelial ovarian cancer, i.e., an antibody for detection of a glycosyltransferase β1,6-N-acetylglucosaminyltransferase 5B as an epithelial ovarian cancer marker. The antibody recognizes, as an epitope, a part of a polypeptide of the enzyme consisting of the amino acid sequence represented by SEQ ID NO: 1.