A backlight device includes LEDs, a light guide plate, an LED substrate, an optical sheet, and a low light-transmissive member. The light guide plate includes a light entering end surface, a light exiting plate surface, and an opposite plate surface. The LED substrate is disposed such that at least a section of the LED substrate overlaps a light entering-side edge section that is an edge section of the light guide plate on the light entering end surface side. The optical sheet includes a light entering-side edge section overlapping section disposed on the light exiting plate surface side of the light guide plate to overlap the light entering-side edge section. The low light-transmissive member disposed on the light entering-side edge section overlapping section of the optical sheet. The low light-transmissive member has a light transmissivity lower than that of other sections of the optical sheet.