Disclosed is a digital X-ray image detector using an FED, including an upper substrate and a lower substrate disposed to face each other; an anode formed beneath the upper substrate; a photoconductive layer formed beneath the anode for forming electron-hole pairs using X-rays; a cathode formed on the lower substrate; an emitter formed on the cathode for emitting electrons of the cathode; a gate electrode formed on an insulating layer provided around the emitter on the cathode; and a data processing part for converting information about the electron-hole pairs formed in the photoconductive layer by the X-rays, transferred from the anode, to digital data through signal processing including filtering, amplification, storage, or A/D conversion. The high performance digital X-ray image detector of this invention has a high image resolution and a large area, is easy to manufacture and process compared to conventional processes, and has excellent detection efficiency of electrical signals.