To provide a back light for a display sheet capable of switching and lighting white light and colored light for making characters or the like of the display sheet emit light by efficiently using LEDs having a plurality of colors.

The back light for the display sheet is provided with a plurality of sections 7a to 7c and luminous bodies arranged in respective sections 7a to 7c. Each luminous body consists of a plurality of LEDs emitting light of a plurality of colors which make white color by additive color mixture, and at least a light diffusing sheet 8 is arranged between these LEDs and the display sheet 5. LEDs are arranged like a polygon in the plane view. The display sheet 5 having characters, graphics, or symbols displayed thereon correspondingly to sections 7a to 7c is irradiated from behind by luminous bodies in respective sections 7a to 7c to transmissively light the characters, graphics, or symbols. Since LEDs emitting light of the plurality of colors are combined and lit and white light is obtained by additive color mixture, LEDs can be efficiently used. When partial LEDs are lit, colored light can be obtained.