An input device provides control information to a host device and including a plurality of keys, a division module and a control module is disclosed. When an object presses a specific key, the specific key generates a resistance value according to a force applied by the object. The division module receives the resistance value and generates a voltage level according to the resistance value and a first level. The control module generates the control information according to the voltage level. The host device executes a function corresponding to the specific key according to the control information.