A display device is provided. The display device includes a signal receiving unit which receives an image signal including a left image and a right image; a signal processing unit which processes the image signal received by the signal receiving unit; a display unit which displays a three-dimensional image based on the image signal processed by the signal processing unit; a user input unit which receives user input regarding an operation mode of the three-dimensional glasses; a synchronizing signal output unit which outputs a synchronizing signal to open and close the left shutter and the right shutter of the three-dimensional glasses corresponding to the left image and the right image, respectively; and a controller which controls the synchronizing signal output unit to output the synchronizing signal based on the operation mode of the three-dimensional glasses obtained from the received user input.