Abstract: A sensing device includes a driving unit, a magnetic transmission unit, a sensing unit, and an operating unit. The magnetic transmission unit includes a main driving wheel, and first and second driven wheels. The main driving wheel includes a main driving wheel body sleeved co-rotatably to the driving unit, a main feedback portion mounted co-rotatably on the main driving wheel body, and a main magnetic driving portion mounted co-rotatably on the main driving wheel body. The first and second driven wheels respectively include first and driven wheel bodies, first and second feedback portions that are mounted co-rotatably and respectively on the first and second driven wheel bodies, and first and second magnetic driven portions mounted co-rotatably and respectively on the first and second driven wheel bodies, and magnetically driven by the main magnetic driving portion to rotate when the main driving wheel body co-rotates with the driving unit.