Structure of insoluble sulfur (Sμ) is linear chain structure which connects sulfur atoms each other. High thermal stable Sμ is indispensable for a rubber vulcanizing agent. High conversion from elemental sulfur (S8) to Sμ is also cost-effective on commercial point of view. Commercial Sμ for a rubber vulcanizing agent has been prepared by quenching of molten sulfur. We prepared Sμ by using melt electrospinning technique. Melt electrospinning method is normally applied to prepare very thin polymer fibers which have high-oriented polymer chains in them. The diameter of the resulted fibrous sulfur was about 20 μm and they showed some rough surfaces. Conversion of Sμ from S8, structure and thermal stability of the melt-electrospun Sμ were also investigated. Higher molten temperature of electrospun process provided higher conversion of Sμ. The conversion of electrospun Sμ was comparable to that of commercial Sμ. The addition of iodine to molten sulfur enhanced the thermal stability of the resulted Sμ under the specific molten temperature; however, this value was lower than that of commercial Sμ. Post-heating process of the melt-electrospun fibrous sulfur was effective for enhancing thermal stability of the electrospun Sμ.