A light guide plate comprises: a plate ember having a light transmitting capability; and a light incidence face provided on a side surface of the plate member; wherein the plate member changes a path of light emitted from a light source arranged to face the light incidence face and emits planar illumination light from an upper surface of the plate member onto an object to be illuminated; wherein an undulated surface portion is formed on the light incidence face. Further, the undulated surface portion is formed by smoothly connecting curved recessed portions and curved raised portions. This arrangement prevents bright lines from being produced near the light source and also prevents brightness variations, thus making uniform an intensity distribution of light that has entered the light guide plate.