Disclosed is an antibody which can bind to GPR49 protein and which has a cell proliferation-inhibiting activity against a cell capable of producing GPR49 protein. The cell proliferation-inhibiting activity may be a cytotoxic activity such as an antibody-dependent cytotoxicity or a complement-dependent cytotoxicity. Also disclosed are: a pharmaceutical composition a cell proliferation inhibitor and an anti-cancer agent, each of which comprises the antibody as an active ingredient. The cancer may be gastric cancer, colorectal cancer, hepatocellular cancer, lung cancer, prostate cancer, ovarian cancer, Ewing sarcoma, or glioma. Further disclosed are: a method for the diagnosis of cancer by detecting GPR49 protein or the expression of a gene encoding GPR49 protein and a diagnosis agent and a kit for use in the method.
