A portable terminal includes an input device and processing hardware which operates a predetermined method. The input device includes a keypad unit consisting of a plurality of key buttons, a board consisting of a plurality of pressure sensors and dome switches for generating signals when pressed, and an actuator for simultaneously pressing the corresponding dome switch and the corresponding pressure sensor when a key button is pressed, with the processing hardware for performing and finishing a first operation based on the signal generated by the corresponding dome switch if generation of the signal generated by the dome switch stops before a valid time has expired, and for performing a second operation based on a pressure change sensed by the corresponding pressure sensor simultaneously pressed until the generation of the signal generated by the corresponding dome switch remains after the valid time has expired.