A sintered indium oxide comprising niobium as an additive, wherein the ratio of the number of niobium atoms relative to the total number of atoms of all metal elements contained in the sintered compact is within a range of 1 to 4%, the relative density is 98% or higher, and the bulk resistance is 0.9 mΩ·cm or less. Provided are a sintered compact of indium oxide system and a transparent conductive film of indium oxide system, which have characteristics of high transmittance in the short wavelength and long wavelength ranges since the carrier concentration is not too high even though the resistivity thereof is low.