Provided is a data input device which is employed in a portable terminal and used as an auxiliary input device. The data input device includes first data input means mounted on a predetermined position of a side surface of the main body of the portable terminal so that a portion of the first data input means is exposed to the outside, and operating when the exposed portion is rotated; second data input means operating when the exposed portion is pressed; a holding unit for maintaining a stopped state of the first data input means; and an elastic sliding unit for returning the second data input means to an initial position.