An object of the present invention is to identify a cancer antigen protein specifically expressed on the surface of cancer cells and provide use of an antibody targeting the cancer antigen protein as a therapeutic and/or prophylactic agent for cancer. A pharmaceutical composition for treating and/or preventing cancer comprising an antibody or a fragment thereof having immunological reactivity with CSPG5 protein consisting of any one of amino acid sequences represented by SEQ ID NOs: 8, 4, 6, 10, and 12 and an amino acid sequence having an amino acid identity of 80% or more to the amino acid sequence, or a fragment thereof consisting of 7 or more consecutive amino acids, as an active ingredient.
