Key input unit and key input method

Disclosed are a digital processing apparatus including a key input unit and a key input method. A key button unit according to the present invention may include: a base that is fixed to the central portion of the key button unit, a slider that moves parallel to the horizontal surface of the base through a user's operation, a frame that supports the parallel movement of the slider, and a restoring unit that provides the resistance force against the parallel movement of the slider and return the parallel-moved slider to the original position thereof. The invention enables the minimization on the number of key buttons by maximizing the number of information that can be inputted through one key button.