A method of displaying windows is provided. The method includes displaying at least two windows, displaying at least one center button disposed at at least one boundary between the at least two displayed windows, determining a window of which the size is to be changed according to a movement direction of the at least one center button, and changing a size of the determined window according to movement of the at least one center button and displaying the determined window having the changed size, wherein the determined window is overlaid on the at least two displayed windows, and wherein a size of the determined window is changed according to movement of the at least one center button.