The present invention provides an antibody for detecting mesothelioma and an antibody having high specificity to mesothelioma and high sensitivity thereto. The present invention also provides a method of diagnosis of mesothelioma by using the antibody, a reagent containing the antibody for use in diagnosis of mesothelioma, and a kit comprising the antibody for use in diagnosis of mesothelioma. Further, the present invention provides a marker for use in diagnosis of mesothelioma. Furthermore, the present invention provides a pharmaceutical composition containing the antibody according to the present invention or an antigen-binding fragment thereof for use in treatment of mesothelioma. An antibody that binds to a glycosylated HEG1 protein obtained from mesothelioma.