Indium tin oxide (ITO) thin films were prepared on quartz glass substrates by a dip-coating process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. The ITO thin films containing 0 similar to 20 mol % SnO2 were successfully prepared by heat-treatment at above 400 degrees C. Chemical stability of sol were investigated by using a FTIR spectrometer. The electrical resistivity of the thin films decreased with increasing heat-treatment temperature, that is carrier concentration increased, and mobility decreased with increasing SnO2 content. The ITO thin films containing 12 mol % SnO2 showed the minimum resistivity of rho = 1.2 x 10(-3) (Omega cm). It also showed high carrier concentration of N = 1.2 x 10(20)(cm(-3)) and mobility mu(H) = 7.0(cm(2)V(-1)s(-1)).