An improved illumination device shortens a redundant area of insufficient light intensity close to a longitudinal end thereof. The device includes a casing, a bar-shaped light guide housed in the casing to cause a light-emitting surface thereof to be exposed, a light-emitting unit secured to an end section of the casing, wherein light from the light-emitting unit is introduced into the bar-shaped light guide through the end face thereof and is totally reflected within the bar-shaped light guide to be emitted through the light-emitting surface, and a shielding section provided to cover an end section of the bar-shaped light guide including the redundant area at the end section of the casing close to the light-emitting unit. A notch is formed at the end section of the bar-shaped light guide on the light-emitting surface side close to the light-emitting unit, and light from the light-emitting unit is reflected on a rear surface of the shielding section through a gap between this notch and the light-emitting unit to be introduced into the bar-shaped light guide.