This invention provides an antibody targeting a cancer antigenic protein specifically expressed on the surface of cancer cells and use thereof in a therapeutic and/or preventive agent for cancers. Specifically, this invention provides an antibody or a fragment thereof which has immunological reactivity with a partial CAPRIN-1 polypeptide consisting of the amino acid sequence represented 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 cancers, comprising the antibody or fragment thereof as an active ingredient.