An input device and a method of switching an input mode of the input device are provided. The input device includes a main body, a state detecting module, a touchpad and a control unit. The main body includes a top surface, a bottom surface and a side surface connected the bottom and top surfaces. The state detecting module includes a first state detecting unit disposed at the bottom surface and a second state detecting unit disposed at the side surface. The first and second state detecting units detect a using state of the input device and generate first and second detecting signals, respectively. The control unit is electrically connected to the state detecting module and the touchpad, and the control unit switches the touchpad to a first control mode or a second control mode according to the first and second detecting signals.