To provide a backlight device with little risk of having a diffusion plate damaged, even if a diffusion plate and a protrusion for maintaining a distance between the plate and a light source come in strong contact with each other or collide with each other due to vibration and fall.

The backlight device 2 includes one or a plurality of light sources 8 arranged at a rear side of a liquid crystal panel 1 having a display screen on the surface, retaining tools 16 retaining the light sources 8, and a diffusion plate 3 arranged between the crystal panel 1 and the light sources 8 for diffusing light irradiated from the light sources 8 and uniformly irradiating it on the crystal panel 1. The retaining tools 16 includes one or a plurality of protrusions 9 for maintaining a distance between the light sources 8 and the diffusion plate 3 at a given value or more. Each protrusion 9 has its tip part covered with a member 10 softer than a material of the diffusion plate 3.