We fabricated ZnO thin film successfully by using RF magnetron sputtering and investigated its potential for being utilized as the key material of piezoelectric device with the characterization of ZnO thin film such as such as crystallinity, surface morphology, c-axis orientation, film density. In thin study, $Ar/O_2$ gas ratio is fixed 70/30, RF power 125W, working pressure 8mTorr, distance between substrate and target 70mm, but the substrate temperature is varied from room temperature to $400^{circ}C$. The relative intensity ($I_{(002)}/I_{(100)}$) or (002) peak in ZnO thin film deposited at $300^{circ}$ was exhibited as 94%, then its FWHM was $0.571^{circ}C$. Also, from the surface morphology evaluated by SEM and AFM, the film deposited at $300^{circ}C$ showed uniform particle shape and excellent surface roughness of 4.08 m. The tendency of ZnO thin film density was exhibited to be denser with increasing substrate temperature but slightly decreased at near $400^{circ}C$.