The present invention provides a method for manufacturing a backlight including a plurality of LEDs arranged in a plane manner. The method includes: preparing LEDs which are classified into a plurality of ranks in accordance with brightness; mounting, in respective blocks each having a same number of points for mounting LEDs, LEDs which are at least two different-ranked; and causing combinations of ranks of the LEDs in the respective blocks to conform to each other. Alternatively, the LEDs, classified into ranks each having a known center value of brightness, are mounted in the blocks such that a total of the center values of the respective ranks in each of the blocks becomes substantially uniform. This realizes a backlight having a uniform in-plane brightness distribution with a merit of cost.