We have investigated the structural, electrical and optical properties of Ga-doped ZnO (GZO) thin films prepared by RF magnetron sputtering with laboratory-made ZnO targets containing 1, 3, 5, 7 wt% of Ga2O3 powder as a doping source. The GZO thin films show the typical crystallographic orientation with c-axis regardless of Ga2O3 content in the targets. The 3,000 Å thick GZO thin films with the lowest resistivity of 7×10-4 Ω·cm are obtained by using the GZO (Ga2O3= 5 wt%) target. Optical transmittance of all films shows higher than 80% at the visible region. The optical energy band gap for GZO films increases as the carrier concentration (ne) in the film increases.