Ga-doped ZnO (GZO) films were deposited by an RF magnetron sputtering method on glass substrates using ZnO as a target containing 5 wt% Ga₂O₃ powder (for Ga doping). The structural, electrical, and optical properties of the GZO thin films were investigated as a function of the substrate temperatures. The deposition rate decreased with increasing substrate temperatures from room temperature to 350℃. The films showed typical orientation with the c-axis vertical to the glass substrates and the grain size increased up to a substrate temperature of 300℃ but decreased beyond 350℃. The resistivity of GZO thin films deposited at the substrate temperature of 300℃ was 7×10^-4 Ωcm, and it showed a dependence on the carrier concentration and mobility. The optical transmittances of the films with thickness of 3,000 Å were above 80% in the visible region, regardless of the substrate temperatures.