Indium tin oxide (ITO), a transparent conductive oxide, is a wide band gap compound semiconductor with a cubic bixbyte structure. Sn-doped indium oxide (10) thin films (In:Sn=90:10) were deposited on microscope glass substrates by a sot-gel spin coating technique. The precursor solution was prepared by mixing indium (111) nitrate pentahydrate (In(NO3)(3)(.)5H(2)O) and tin (IV) chloride bis(2,4-pentanedionate) (SnCl2(C5H7O2)(2) dissolved in acetic acid and acetone mixture. Crystalline ITO thin films were obtained after an annealing process at temperatures between 450degreesC-550degreesC for one hour. The microstructure and optical properties of ITO films were investigated as function of annealing temperature. XRD analysis revealed single phase In2O3 (JCPDS 06-0416). The optical transmittance of the films in the visible range was more than %80. The direct optical band gap of ITO films was measured between 3.7-3.9 eV.