A planar light-emitting device has a plurality of light-emitting units each including a light source and a lightguide plate. The light-emitting units are arranged with the light-exiting surfaces of their respective lightguide plates being substantially flush with each other. Each lightguide plate has an upper surface as a light-exiting surface, a lower surface opposite to the light-exiting surface, and a peripheral side surface extending between the respective peripheral edges of the upper and lower surfaces. The lightguide plate emits light received from the light source from the light-exiting surface. At least a part of the peripheral side surface is an inclined surface inclined relative to the light-exiting surface.