An ultra-sensitive gas sensor using semiconductor oxide nanofibers and a method of fabricating the same are provided. The gas sensor includes an insulating substrate, a metal electrode formed on the insulating substrate, and a semiconductor metal oxide nanofibers layer formed on the metal electrode and having nanoparticles of high sensitivity coated thereon. The method of fabricating a semiconductor oxide nanofibers gas sensor includes fabricating an oxide using a solution for electrospinning, electrospinning the solution, performing an annealing process to form an oxide semiconductor nanofiber, and partially coating a nano-sized metal oxide or metal catalyst particle having high sensitivity to a specific gas on a surface of the nanofiber having a large specific surface area. As a result, a semiconductor oxide nanofibers gas sensor having ultra sensitivity, high selectivity, fast response and long-term stability can be fabricated.