A planar light source device includes a light source body, and first and second electrodes. The light source body includes a first substrate, a second substrate facing the first substrate, and partitions disposed between the first and second substrates to define a discharge space. The first electrode includes a first voltage applying portion and a first electrode portion having protrusions extended from the first voltage applying portion and disposed between the partitions. The second electrode is disposed on the light source body, such that the second electrode is spaced apart from the first electrode. The planar light source device generates light having uniform luminance distribution.