A wheel device applied to a mouse includes a base, a wheel module, a sheltering component and an optical detecting module. The base has a holder. The wheel module is disposed on the base and includes a roller and a wheel. The roller includes a rolling surface, an axle and a plurality of rib structures. The axle is rotatably disposed on the holder in an axle direction. The rib structures are disposed inside the rolling surface. The wheel is disposed on the rolling surface of the roller. The sheltering component includes light sheltering areas and light penetrating areas disposed on the roller or the wheel and around the axle direction. Each light sheltering area is perpendicular to the axle. The optical detecting module has an optical emitter and an optical receiver. The optical receiver is adapted to receive an optical signal emitted by the optical emitter.