This invention provides an antibody targeting a cancer antigenic protein specifically expressed on the surface of cancer cells and use thereof as a therapeutic and/or preventive agent for cancer. More specifically, the present invention provides an antibody, or a fragment thereof which has immunological reactivity with a CAPRIN-1 protein, the antibody comprising a heavy chain variable region comprising complementarity determining regions of SEQ ID NOs: 5, 6, and 7 and a light chain variable region comprising complementarity determining regions of SEQ ID NOs: 9, 10, and 11, and a pharmaceutical composition for treatment and/or prevention of cancer, comprising the same as an active ingredient.
