1. A handwriting input method of a portable terminal device using a touch pen, the handwriting input method comprising: displaying an execution screen of an application on a touch screen in response to the application being executed; overlapping a handwriting input layer, which is configured for a handwriting input, with the execution screen; inputting a handwriting image on an area of the handwriting input layer using the touch pen; determining a data type for recognizing the input handwriting image in consideration of an attribute of the area corresponding to a position in which the handwriting image has been input on the execution screen, and recognizing the input handwriting image as the determined data type; and applying a recognized result of the determined data type to the application.