Provided is a high density gallium oxide-zinc oxide series sintered body sputtering target for forming a transparent conductive film containing 20 to 500 mass ppm of aluminum oxide. In a gallium oxide (Ga2O3)-zinc oxide (ZnO) series sputtering target (GZO series target) for forming a transparent conductive film, trace amounts of specific elements are added to obtain a target capable of improving the conductivity and the bulk density of the target; in other words, capable of improving the component composition to increase the sintered density, inhibit the formation of nodules, and prevent the generation of an abnormal electrical discharge and particles. Also provided are a method for forming a transparent conductive film using such a target, and a transparent conductive film formed thereby.