A discharge lamp unit constitutes circuit components including self-heating components that radiate the heat, i.e., a circuit board and a DC/DC transformer, and a heat radiation member. The heat radiation member made of metal is arranged in a portion between the self-heating components and the other components, so as to cover at least a portion of the self-heating component. In the discharge lamp unit, the heat produced by the self-heating components can be absorbed by the heat radiation member before the conducting heat reaches the circuit components other than the self-heat components. As a result, the heat produced by the self-heating components can be effectively radiated away.