The purpose of this paper is that the roughness(Rrms = 31$AA$, Rp-v = 270$AA$) of ITO thin film deposited by sputtering method for OELD is improved to Rrms $leq$ 10$AA$, Rp-v $leq$ 80$AA$ by chemical mechanical polishing(CMP). First, ITO thin films are polished with a variety of consumables (Pads, Slurries) to choose proper some for the roughness improvement and the CMP mechanism of ITO thin films is demonstrated on the ground of the experiment results. Henceforth, the CMP characteristics (Removal rate, Non-uniformity) of chosen consumables are evaluated according to processing conditions (Polishing pressures, Table velocities) and suitable conditions for ITO film CMP are selected. Finally, the electrical and optical properties (Sheet resistance, Transmittance) of ITO thin films are investigated to verify whether or not ITO thin film are still suitable for OELD after polished.