An input device includes a wheel supporting structure, a scroll wheel, a hook part, a linking part, and a switching mechanism. The scroll wheel is rotatably supported by the wheel supporting structure, is exposed from the input device, and has a rotary shaft with a plurality of toothed slots thereon. The hook part is disposed biased on the wheel supporting structure to selectively engage with the toothed slots. The linking part is pivotally connected to the wheel supporting structure. The switching mechanism includes an abutting part and a switching part. The abutting part abuts against the linking part. The switching part is coupled to the abutting part. Therein, the switching mechanism is operable to move the abutting part through the switching part to rotate the linking part to abut against and move the hook part to disengage from the toothed slots.