A heat-dissipating fan includes a casing, a stator, and an impeller. The casing includes a base supported by a plurality of ribs. The base includes an axial tube for receiving a bearing through which a shaft extends. Vanes are provided on an outer circumferential wall of the impeller. An end of the shaft is fixed to an axial seat at a center of the impeller. A magnetic member is mounted to the other end of the shaft. The magnetic member and the impeller rotate synchronously under magnetic induction. When the heat-dissipating fan is mounted on top of a heat-dissipating device, a propeller of the heat-dissipating device is driven to turn synchronously under magnetic attraction. When air currents are driven by the vanes to flow downward, great noise resulting from tangential wind effect is avoided, as the ribs are not in the air inlet area.