The invention provides an input device including a holder, a first wheel, a slider, and a first pressure part. The first wheel is disposed on the holder, and includes a side surface, a circle center, and a segment adjusting structure. The segment adjusting structure is disposed on the side surface in a manner of surrounding the circle center. The slider is disposed on the holder, and is movable relative to the holder to move toward or away from the circle center. The first pressure part includes two first ends. One of the first ends is connected to the slider, and as the slider moves toward or away from the circle center, interference between the other first end and the segment adjusting structure is increased or reduced.