In the case that the LED is used as a light source for a backlight such as a display unit or the like, if a lot of current is circulated for securing a brightness, a lot of heat is generated in view of a characteristic of the LED, so that the LED comes to a high temperature, and there is a problem that the characteristic of the LED itself is deteriorated such as a light output is lowered, a long-term service life can not secured, or the like. Further, in the case that a temperature difference exists between a plurality of LEDs, there is a problem that it appears as a brightness irregularity of a screen of the display unit. The display unit is provided with a heat sink attached so as to be thermally contacted with an opposite side to an LED mounting surface of a substrate on which the LEDsare mounted, and one or a plurality of fans, a base portion of the heat sink has a substrate mounting surface and a fin constituting surface, the fin constituting surface is approximately perpendicular to the substrate mounting surface, and the fin constituting surface of the base portion and an air supply and exhaust surface of a cooling air are formed in an opposite side to a screen display side of the display.