The ITO films were deposited on polyethylenenaphthalate at the room temperature using dc magnetron sputtering system with Ar ion-beam assist. The dc sputtering power was maintained at 200 W, and the Ar ion-beam power was varied from 20 to 70 W. The change in the resistance of the ITO films in the cyclic bending tests was significantly delayed with the Ar-ion-beam power 40 W. Also, the ITO film showed relatively low resistivity (5.39 x 10(-4) Omega cm). Thus. the ITO film showed good mechanical and electrical properties attributable to the effect of Ar ion bombardment on the thin film formation.