The present invention provides novel antibodies that recognize the extracellular domain of a human CLCP1 antigen; nucleic acids encoding the antibodies; vectors carrying the nucleic acids in an expressible manner; transformed cells containing the vectors; methods for producing the antibodies; diagnostic methods for cancer or prognosis of cancer, immunohistological or immunocytological assay methods, and kits for determining the expression level of CLCP1 in cells or tissues, all of which use the antibodies; pharmaceutical compositions comprising the antibodies; agents for treating or preventing CLCP1-expressing cancer; agents for inhibiting growth, migration, invasion, or metastasis of CLCP1-expressing cancer cells; immunostaining agents for staining CLCP1-expressing cancer cells; and agents for treating or preventing CLCP1-expressing tumor. The present invention also provides methods of screening for candidate substances that inhibit cancer cell growth, invasion, migration, or metastasis, or candidate substances having cytotoxicity against cancer cells.