An input device disposed on a circuit board is provided. The input device includes a frame, a sliding base, a rotary wheel, and a switch. The sliding base is slidingly connected to the frame. The sliding base substantially slides linearly along a slide axis. The slide axis is substantially parallel to the circuit board. The rotary wheel is revolvably affixed to the sliding base. The rotary wheel is substantially rotates around a rotation axis. The rotation axis is substantially perpendicular to the circuit board. The switch is disposed on the frame. The rotary wheel actuates the switch through the sliding motion of the sliding base. Accordingly, some merits of said input device include smaller volume, easy assembling and better durability.