To improve appearance by suppressing a luminance reduction at gaps between end faces adjacent to each other even when a plurality of light guide plates are aligned in a planar light source and a liquid crystal display device.

The planar light source 1 is constituted by aligning a plurality of light units 4 in a plurality of rows in such a state that light guide plates 3 are arranged adjacently to each other, wherein each of the light units 4 includes an LED light source 2 and one of the light guide plates 3 for discharging a planar light from a main face side 3b by changing the optical path of the light entering from the LED light source 2 and guided, the LED light source 2 being disposed at an end face 3a of a base end side which is a light incident face, and each of the end faces 3c of the light guide plates 3, which are disposed adjacent to one another except at the end face 3a of the base end side, is inclined to the main face 3b.