A vehicle’s drag-reducing apparatus, adapted to be arranged at the tail end of a vehicle, includes a diversion body positioned at the lateral surface of the vehicle and a rotary piece. The VCO includes a parallel LC circuit having multiple fixed capacitors that can be switched-in or switched-out of the LC circuit according to a capacitor control signal to perform band-select tuning of the VCO. Furthermore, a light-emitting device with high reliability including such a sealed body is provided.