Cooling apparatus of discharge lamp

1. A cooling apparatus of a discharge lamp, the discharge lamp is composed of a base holding cover having a base on which an external power source is applied; a lamp holding cover for holding and supporting a plurality of lamps, an electronic ballast which converts the external power source into a power source for turning on the lamps, a heat emitting cover interposed between the base holding cover and the lamp holding cover, in which a plurality of heat radiating openings are formed so as to emit the radiated heat by a heat spreading plate into the outside, the heat spreading plate attached to the electronic ballast, a cooling fan to cool the heat radiated to the heat spreading plate, the electronic ballast comprising a thermostat wherein a thermal switch in said thermostat extinguishes the external power source upon exceeding a certain predetermined temperature and wherein the cooling fan is connected with the thermostat in parallel so as to drive the cooling fan by means of the thermostat when the temperature reaches a certain predetermined temperature, wherein the heat spreading plate further comprises cooling pins directly connected to a plurality of transistors embedded into the electronic ballast.