To provide a method for manufacturing fine powder of hexagonal indium oxide or fine powder of hexagonal indium oxide containing tin, which are suitable for forming a sintered body for vacuum film deposition, by which an ITO film having a stable transparency and an excellent conductivity or a heat-shielding performance is obtainable, and suitable for a coating method or a method for dispersing in a resin as well.

The fine powder of hexagonal indium oxide or hexagonal indium oxide containing tin is manufactured by treating indium oxide hydrate or a mixture of tin oxide hydrate and indium oxide hydrate at 150-350°C in an atmosphere from oxygen-less to low oxygen and then thermally decomposing at 360-1,200°C.