To provide: agents that target B7-H4 for diagnosis and treatment of B7-H4-associated conditions, such as cancer; and methods of using the same.SOLUTION: The present invention provides: an isolated antibody and a humanized antibody that bind to B7-H4; an immunoconjugate comprising the anti-B7-H4 antibody and a cytotoxic agent; a method of treating an individual having a B7-H4-positive cancer; a method of inhibiting proliferation of an B7-H4-positive cell; a method of detecting human B7-H4 in a biological sample; and a method for detecting an B7-H4-positive cancer.SELECTED DRAWING: Figure 17【課題】がんのようなB7-H4付随状態を診断及び治療するための、B7-H4を標的にする薬剤、並びにその使用方法の提供。【解決手段】B7-H4に結合する単離抗体およびヒト化抗体。抗B7-H4抗体と細胞傷害剤とを含むイムノコンジュゲート。B7-H4陽性のがんを有する個体を治療する方法。B7-H4陽性細胞の増殖を阻害する方法。生体試料においてヒトB7-H4を検出する方法。B7-H4陽性のがんを検出するための方法。【選択図】図17