To provide: a low cost illuminating device excellent in a light-emitting quality; a method of manufacturing the same; and a display device using the illumination device.

In the illuminating device which includes a cold-cathode fluorescent tube (a light source) and a diffusing plate 15 for diffusing light from the cold-cathode fluorescent tube, a convex part 15b1 and a concave part 15b2 are arranged on a surface 15b of the diffusing plate 15 on a side of the cold-cathode fluorescent tube. Then, in the illuminating device, there is formed a reflecting part 21 for reflecting the light on a side of the cold-cathode fluorescent tube against the convex part 15b1 of the diffusing plate 15.