We have prepared spherical and plate-like bismuth nano-particles by the polyol process. The sphere size was varied from 200 to 400 nm by the addition of polyvinylpyrrolidone to inhibit the aggregation of atoms. Nano-plates 800 nm wide and 50 nm thick were formed by adding a probe-level ferric chloride. The crystal axis of the nano-spheres (diameter: 350 ± 50 nm) dispersed in polysiloxane was oriented under high magnetic fields because of the anisotropic susceptibility of bismuth. The anisotropic susceptibility was estimated as 3.6 × 10-5 from a numerical simulation of the field dependence of the (110) peak in the XRD pattern. The value was slightly smaller than that for a bulk single crystal. Composites of bismuth nano-spheres and plates dispersed in poly(methyl methacrylate) were prepared under high magnetic fields. The composites showed different transmittance depending on whether the direction of the propagation of light was parallel or perpendicular to the applied magnetic field, because of the anisotropy of the dielectric constants and the shape of the nano-plates.