A portable terminal including: a controller receiving signals corresponding to a plurality of input buttons and outputting image data to be displayed on the plurality of input buttons using the received signals; and a plurality of buttons for inputting a key from a user and outputting a signal corresponding to the key pressed, and for receiving the image data from the controller and displaying the received image data. By using the display buttons for displaying variable images corresponding to specific functions as well as an essential function of inputting keys from a user when a specific function is input in the portable terminal, a plurality of functions can be input with only a few buttons, providing speed and convenience to the user for function input.