A discharge lamp lighting device comprising a lamp socket for connecting the discharge lamp; a stabilizing circuit connected to the power source and outputting a voltage to the lamp socket; a starting circuit connected between the stabilizing circuit and the lamp socket, and activated before the discharge lamp begins discharging to generate a high voltage required to start discharging, and deactivated after discharging begins; and a means for disabling the starting circuit when the discharge lamp is not installed in response to the installation or non-installation of the discharge lamp to the lamp socket.Preferably, the starting circuit is integrated with the lamp socket, thus forming a lamp socket unit comprising a starting circuit.