The present invention is an embolization coil having an optimum morphological stability. The embolization coil includes a wire material made of an Au-Pt alloy. The wire material constituting the embolization coil has such a composition that a Pt concentration is 24 mass% or more and less than 34 mass%, with the balance being Au. The wire material has such a material structure that a Pt-rich phase of an Au-Pt alloy having a Pt concentration of 1.2 to 3.8 times a Pt concentration of an α phase is distributed in an α phase matrix. The wire material has a bulk susceptibility of-13 ppm or more and -5 ppm or less. In a material structure of a transverse cross-section of the wire material, an average value of two or more average crystal particle diameters measured by a linear intercept method is 0.20 µm or more and 0.35 µm or less.
