A multi-functional human interface device includes a control unit and a first multi-functional input button. The first multi-functional input button includes a cover unit configured to receive a touch input of a user's finger, an electrode unit including a transmitter and a receiver to form an electric field, an elastic unit configured to move from a first height to a second height when a first pressure is applied from the cover unit and configured to move back to the first height when the first pressure from the cover unit is released, and a switch unit configured to generate an electric signal representing an input of a predetermined letter.