A surface light source device (2) includes a plurality of electron sources (20), a plurality of magnetic coils (201), and an anode (22). Each electron source includes two cathodes (203) and at least one filament (202). The two cathodes face to each other and define therebetween a space (200) having a first opening (207) and a second opening (208). The second opening faces to and is larger than the first opening. The at least one filament is located at the second opening and is configured for emitting electrons to escape the space from the first opening. Each magnetic coil is located at one second opening. The anode includes a transparent electrically conductive layer (222) and a phosphorescent layer (221). The phosphorescent layer faces towards the plurality of electron source. The present surface light source device can achieve high brightness and is environmentally friendly.