The lighting device according to the present invention is used for lighting a light source device. The light source device includes a light source unit connected between first and second power supply terminals and a first impedance device which has an impedance associated with an electric property of the light source unit and is connected to the second power supply terminal. The lighting device performs a first process and a second process. In the first process, the lighting device obtains a measurement indicative of the impedance by supplying power to the first impedance device via the second power supply terminal while prohibiting output of DC power for lighting, and determine an operating condition based on the measurement. In the second process, the lighting device operates so that the DC power for lighting satisfies the operating condition.