A structure of a TFT substrate for a high resolution digital x-ray detector, in which two TFT substrates are arranged to be a double substrate by overlapping each other such that an upper plate is moved ½ pixel distance with respect to a lower plate in a direction along one axis. Thus, a difference in movement between the upper and lower plates is a ½ pixel distance. Also, two virtual pixels are obtained from one pixel. Three TFT substrates are arranged to be a triple substrate by overlapping one another such that a middle plate is moved a ½ pixel distance with respect to a lower plate in a direction along an X axis and an uppermost plate is arranged by being moved a ½ pixel distance with respect to the lower plate in a direction along a Y axis. Thus, resolution is increased as data of one pixel is divided into four data to be analyzed and an measured value of a pixel of each overlapping substrate is compared.