A device for emitting white-color light comprising: (i) a light emitting diode display device including: a plurality of light emitting diode chips which emit visible light of a blue color and comprise a gallium nitride compound semiconductor containing indium; and a phosphor capable of absorbing a part of the blue color light and emitting a light having longer main emission wavelength than the main emission peak of said LED chips, wherein said phosphor comprises a garnet fluorescent material activated with cerium, which contains at least one element selected from Y, Lu, Sc, La, Gd and Sm, and at least one element selected from Al, Ga and In, the blue color light and the light from said phosphor being mixed to make the white-color, of which chromaticity point is on a straight line connecting a chromaticity point of the blue color light and a chromaticity point of the light from said phosphor, and a transparent material covering said LED chips and containing said phosphor, (ii) a gradation control unit for converting display data to pulse signals, and (iii) a driver receiving said pulse signals from said gradation control unit to drive said LED chips of the LED display device, wherein the gradation control unit is adapted to compute a duration of turning on each of the LED chips according to the display data, and output the pulse signals for turning on and off the LED chips to the driver, so that the brightness of the white-color light from each of the LED chips is controlled according to the display data. (i) a light emitting diode display device including: a plurality of light emitting diode chips which emit visible light of a blue color and comprise a gallium nitride compound semiconductor containing indium; and a phosphor capable of absorbing a part of the blue color light and emitting a light having longer main emission wavelength than the main emission peak of said LED chips, wherein said phosphor comprises a garnet fluorescent material activated with cerium, which contains at least one element selected from Y, Lu, Sc, La, Gd and Sm, and at least one element selected from Al, Ga and In, the blue color light and the light from said phosphor being mixed to make the white-color, of which chromaticity point is on a straight line connecting a chromaticity point of the blue color light and a chromaticity point of the light from said phosphor, and a transparent material covering said LED chips and containing said phosphor, a plurality of light emitting diode chips which emit visible light of a blue color and comprise a gallium nitride compound semiconductor containing indium; and a phosphor capable of absorbing a part of the blue color light and emitting a light having longer main emission wavelength than the main emission peak of said LED chips, wherein said phosphor comprises a garnet fluorescent material activated with cerium, which contains at least one element selected from Y, Lu, Sc, La, Gd and Sm, and at least one element selected from Al, Ga and In, the blue color light and the light from said phosphor being mixed to make the white-color, of which chromaticity point is on a straight line connecting a chromaticity point of the blue color light and a chromaticity point of the light from said phosphor, and a transparent material covering said LED chips and containing said phosphor, (ii) a gradation control unit for converting display data to pulse signals, and (iii) a driver receiving said pulse signals from said gradation control unit to drive said LED chips of the LED display device,