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 partial CAPRIN-1 polypeptide consisting of the amino acid sequence shown by SEQ ID NO: 5 or an amino acid sequence having 80% or higher sequence identity to the amino acid sequence, and a pharmaceutical composition for treatment and/or prevention of cancer comprising the same as an active ingredient.