Disclosed is a monoclonal antibody binding to an ITM2A protein. This antibody is useful in the diagnosis, prevention, and treatment of cancer such as Ewing's sarcoma, T cell leukemia, T cell lymphoma, acute myeloid leukemia, B cell tumor, and multiple myeloma. The present invention also provides a pharmaceutical composition, a cell growth inhibitor, and an anticancer agent containing the antibody as an active ingredient, and a method for treating cancer, a method for predicting the efficacy of cancer treatment, and a method for determining the presence of cancer in a test subject using the antibody.
