In this study, we have fabricated a fiber-optic dosimeter using an organic scintillator and a plastic optical fiber for measuring percentage depth dose with high energy X-ray beam. The scintillating light generated in organic sensor probe embedded in a solid water are guided by 20 m plastic optical fiber to the light-measuring device such as a photodiode- amplifier system. Using a fiber-optic dosimeter and an ion chamber, percentage depth dose curves are measured with 6 and 15 MV energies of X-ray beam whose field sizes are 2 cm ?2 cm and 10 cm ?10 cm.