An embolization coil, which is constituted of a wire rod composed of a Au-Pt alloy. The wire rod has a composition of Pt concentration of not less than 24 mass% but less than 34 mass% and the balance being Au. The wire rod has a material texture in which distributed in an α-phase matrix is a Pt-rich phase made of a Au-Pt alloy having a Pt concentration of 1.2 to 3.8 times of the Pt concentration of the α-phase. The wire rod further has a bulk susceptibility of not less than -13 ppm and not more than -5 ppm, and an average value of two or more average grain sizes measured by linear analysis with respect to a cross-section in the transverse direction of the material texture is not less than 0.20 μm and not more than 0.35 μm. The embolization coil has a good shape stability.本發明提供一種形態安定性良好的栓塞用線圈,係以由Au-Pt合金所成的線材構成的栓塞用線圈;構成前述栓塞用線圈的前述線材,係具有Pt濃度24質量%以上且未滿34質量%、其餘部分為Au的組成,且具有在α相基質中,分布有由相對於α相之Pt濃度為其1.2倍至3.8倍的Pt濃度的Au-Pt合金所構成的富Pt相的材料組織;前述線材其體積磁化率為-13ppm以上且-5ppm以下;更且,前述線材,係在其短邊方向剖面的材料組織中,藉由線性分析法所測定到之2個以上之平均結晶粒徑的平均值成為0.20μm以上且0.35μm以下。
