Method for displaying three-dimensional image and display apparatus for performing the same

PURPOSE: A 3D image display method and a display device performing the same increase the brightness of a display panel by converting the gradation of image data displayed on the display panel. CONSTITUTION: A panel driving unit (200) outputs a converted left-eye image having a smaller gradation than a left-eye image to a first pixel based on the left-eye image during a first period and outputs the left-eye image to the first pixel during a second period. The panel driving unit outputs a converted right-eye image to have a smaller gradation than a right-eye image to the first pixel based on the right-eye image during a third period and outputs the right-eye image to the first pixel during a fourth period. [Reference numerals] (210) Frame rate altering unit; (220) Timing controlling unit; (230) Gate driving unit; (240) Data driving unit; (400) Light source driving unit