The present invention discloses an antibody that targets a cancer antigen protein expressed specifically on the surface of cancer cells, and the application of the antibody in a treatment and/or preventative agent for said cancer. Specifically disclosed are: an antibody or a fragment thereof, said antibody being immunologically reactive with a partial polypeptide of CAPRIN-1 comprising the amino acid sequence represented by SEQ ID NO: 5 or an amino acid sequence having 80% or more sequence identity to the amino acid sequence represented by SEQ ID NO: 5； and a pharmaceutical composition for the treatment and/or prevention of cancer, said pharmaceutical composition being characterized by containing, as an active ingredient, the antibody or a fragment thereof.La presente invención se refiere a un anticuerpo o un fragmento del mismo, caracterizado porque se une a un polipéptido CAPRIN-1 parcial que consiste de la secuencia de aminoácidos representada por ala Glu Gln Lys Arg Leu Lys Thr Val Leu Glu Leu Gln Tyr Val Leu (SEQ ID NO: 5).
