Zirconium fluoride (ZrF4 ) thin films were formed by plasma CVD and evaporation for thin-film optical wave guide. In the case of plasma CVD, ZrF4 compound was actually observed to be synthesized from the vapour of Zr and CF4 gas according to. ESCA measurement, even if the film contained impurities. As for evaporation, transparent and amorphous film was obtained and optical transmission loss was measured by scattering detection method, and the loss was calculated to be 9.5 dB/cm. But when only ZrF4 was deposited, thin film was tarnished to be white because of adsorption of moisture. Therefore, simultaneous evaporation of ZrF4 and BaF2 was performed and the charastaristic was stabilized.