A lighting device includes first to third output terminals, a power converter, a bypass switch, and a controller. A first light source is connected between the first and third output terminals. A second light source is connected between the second and third output terminals. The bypass switch is connected between the second and third output terminals. The controller switches the bypass switch between ON-state and OFF-state. The controller controls the power converter to adjust an output current. The controller includes a voltage meter for measuring a voltage corresponding to an output voltage of the power converter. The controller compares a measured voltage of the voltage meter with a first threshold voltage while keeping the bypass switch in OFF-state. The controller compares the measured voltage with a second threshold voltage while keeping the bypass switch in ON-state. The second threshold voltage is smaller than the first threshold voltage.