A method and apparatus for detecting an X-ray, the apparatus includes a detector which comprises a pixel array in which a plurality of pixels for detecting an X-ray transmitted by a body to be examined are arranged in a matrix form, a read-out unit which reads out electrical signals corresponding to the detected X-ray from the pixel array, and a reset controller which controls the pixel array to be reset after the X ray is detected, by performing switching so that the plurality of pixels of the pixel array are commonly connected to the reset power source.