ITO and ITO:Ce films were deposited by DC magnetron sputtering using an ITO ($SnO_2$: 10 wt%) and $CeO_2$ doped ITO ($CeO_2$: 0.5, 3.0, 4.0 and 6.0 wt%) ceramic targets, respectively, on unheated polyethylene terephthalate (PET) substrates. The lowest resistivity $6.7{ imes}10^{-4}{Omega}cm$ was obtained from ITO:Ce film deposited using $CeO_2$ (3.0 wt%) doped ITO target. On hte other hand, ITO:Ce (0.5wt%) film has the excellent mechanical durability which was evaluated by bending test. This result was attributed to the higher binding energy of $CeO_2$ compared to $SnO_2$ and $In_2O_3$. Therefore, $CeO_2$ atoms have a small displacement caused by the bombardment of high energy particles, and it attribute to the increase in adhesion caused by decrease in internal stress. The average transmittance of the films was more than 80% in the visible region.