The effects of the post-deposition annealing on the structural optical properties of sputtered $TiO_2$ thin films were studied; annealing was carried out in air up to $1000^{circ}C$ for different duration. The results of the X-ray diffraction and the raman spectroscopy showed the annealing-condition dependent structural transformation of $TiO_2$ films from the as-deposited amorphous phase to the anatase and rutil phases. The spectroscopic elliposometry was used to investigate the deposition-condition dependence of the as-deposted films optical constants and also the evolution of the optical constants correlated with the annealing-induced structural transformation.