<p>PURPOSE: A pen input device and method thereof is provided to effectively correct a display size without additional cost by performing correction of an handwriting input using a relative coordinate without hardware modification. CONSTITUTION: A touch screen unit(120) includes a display unit (130) and a touch panel(140) for a user handwriting input. The display unit displays various images and state information occurred during operation of a pen input by control of a controller(100). The touch panel outputs a touch signal according to the contact of user to controller. The controller controls handwriting data to be displayed according to the handwriting recognition of user. The controller produces a feature points about handwriting data.</p>
