An X-ray detector capable of independently controlling a read-out rate for each region, an X-ray imaging apparatus having the same, and a method of controlling the same are provided. The X-ray detector includes a plurality of pixels which are two-dimensionally arranged and configured to output an electrical signal corresponding to incident X-rays, a plurality of gate lines configured to connect the plurality of pixels in a row direction, a plurality of data lines configured to connect the plurality of pixels in a column direction, a read-out circuit configured to read out the electrical signal generated by the plurality of pixels through the plurality of data lines, and a switcher configured to independently turn connections between the respective data lines in the plurality of data lines and the read-out circuit on and off.