The present invention relates to a pharmaceutical for treating and / or preventing cancer comprising an antibody against a cancer antigen CAPRIN-1 protein specifically expressed on the surface of a cancer cell and an antitumor agent, together or separately in combination. , As well as its use.この発明は、癌細胞の表面に特異的に発現する癌抗原CAPRIN-1タンパク質に対する抗体と抗腫瘍剤とを、一緒に又は別々に、組み合わせて含む、癌の治療及び/又は予防のための医薬品、並びにその使用、に関する。