PURPOSE: To provide an illuminator and a liquid crystal display device using a light transmission member and increasing the incident quantity of light to the light transmission member, related to the illuminator irradiating with light from a rear surface and the liquid crystal display device using the illuminator.

CONSTITUTION: This device is provided with the flat plane-shaped light transmission member 4 with a prescribed thickness, a light source 2 arranged shifting in the direction of the thickness on the end part of the light transmission member 4 and a light incident surface 42 formed on the light transmission member 4 so that the incident angle of the light emitted from the light source 2 to the light transmission member 4 becomes small. Since the end part of the light transmission member 4 is made a slope being the light incident surface 42 in the illuminator, the beam from the light source 2 is made incident on the inside from the end part of the light transmission member 4 without reflecting by reducing the incident angle.