A key input device for data input means of a device is provided. The key input device includes a first terminal for outputting a key input signal, a second terminal spaced apart from the first terminal and having at least two divided parts, wherein all the divided parts contact the first terminal during a key input operation, at least one resistor allocated to each of the divided parts of the second terminal, connected in parallel to each other, and having respectively different resistance values, and a processor chip for controlling a corresponding key input operation according to respectively different voltage values outputted from the first terminal, by at least one corresponding resistor that is electrically and selectively connected to each of the divided parts.