A surface light source device includes a body, a partition member, a first providing member and a visible light generating unit. The body includes a first substrate having first main and sub regions alternatingly formed with each other, and a second substrate having second main and sub regions facing the first main and sub regions, respectively. The partition member is interposed between the first and second sub regions to form discharge spaces between the first and second main regions. The partition member has a passage connecting between the discharge spaces. The first providing member is disposed on the passage, and the providing member provides the discharge space with operation gas. The visible light generating unit generates a visible light from the operation gas of the discharge spaces. Therefore, process of manufacturing the surface light source device is simplified to enhance productivity.