The present invention provides an alloy for medical use including an Au—Pt alloy, in which the Au—Pt alloy has a Pt concentration of 24 mass % or more and less than 34 mass % with the balance being Au, and has at least a material structure in which a Pt-rich phase having a Pt concentration higher than that of an α-phase is distributed in an α-phase matrix, the Pt-rich phase has a Pt concentration that is 1.2 to 3.8 times the Pt concentration of the α-phase, and the Pt-rich phase has an area ratio of 1 to 22% in any cross-section. This alloy is an artifact-free alloy material that exhibits excellent compatibility with a magnetic field environment such as an MRI and has magnetic susceptibility of ±4 ppm with respect to magnetic susceptibility of water.