Antibodies that bind to a GPR49 protein and have cell proliferation inhibitory activity against cells expressing the GPR49 protein are disclosed. Cell proliferation inhibitory activities are cytotoxic activities such as antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. Pharmaceutical compositions, cell-proliferation inhibitors, and anticancer agents containing an antibody of the present invention as an active ingredient are also disclosed. Examples of cancer include gastric cancer, colon cancer, hepatocellular carcinoma, lung cancer, prostate cancer, ovarian cancer, Ewing's sarcoma, and glioma. Furthermore, methods for diagnosing cancer by detecting expression of a GPR49 protein or a gene encoding a GPR49 protein, and diagnostic agents and kits to be used in these methods are also disclosed.
