This study analyzes the optical characteristics of the ITO thin film deposited using DC magnetron sputtering to study the characteristics of ITO transparent electrodes for organic solar cells deposited by sputtering. For the experiments, the pressure ranged from 1–3 mTorr, and the applied voltage ranged from 260–340 V at 10 V intervals. The results of light transmittance, refractive index, and surface images were analyzed using equipment such as a spectrophotometer, an elliptical polarization analyzer, and a scanning microscope. As a result, under a pressure of at least 1 mTorr, light transmittance of at least 90% was measured, and the refractive index of the thin film had an excellent value of at least 2. Therefore, optimal conditions were established for the application of ITO transparent electrodes for organic solar cells.