Abstract: A discharge-lamp operating apparatus used for operating a discharge lamp includes an outer case having high thermal conductivity and a printed circuit board housed in the case and provided with a discharge-lamp operating circuit including an electromagnetic equipment with a core and a switching element. The electromagnetic equipment is inserted into an opening formed in a part of the circuit board so that the equipment is attached to the circuit board, and the switching element is arranged on the circuit board with it being separated from the equipment so that it is prevented from being influenced by heat generated from the equipment and has a heat radiating member being in face-contact with at least one of the inner surfaces of the case.