The　luminous　environment　is　usually　created　by　daylight　or　artificial　light,　which　are　thought　as　two　different　light　sources　as　they　offers　occupants　different　subjective　feelings.　However,　the　reasons　and　influencing　parameters　are　still　unclear,　and　based　on　the　lab　experiments　with　12　volunteers,　this　study　investigates　diurnal　effects　of　illuminance　level　(300　lx　vs.　500　lx　vs.　1000　lx　at　horizontal　illuminance)　and　spectral　information　(daylight　vs.　daylight　LED　vs.　conventional　LED)　on　the　performances　of　working　memory.　From　the　results,　the　response　speed　of　2-back　test　is　approved　as　an　indicator　for　visual　tasks,　and　both　illuminance　level　and　spectral　information　are　found　have　big　influence　on　response　speed.　The　horizontal　illuminance　at　500　lx　is　found　as　the　best　condition　among　three　levels　within　all　spectral　light　sources,　while　the　conventional　LED　has　the　worst　performance　compared　with　daylight　LED　spectrum　and　daylight　spectrum　at　various　illuminance　levels.　In　conclusion,　daylight　LED,　which　has　both　good　spectral　information　and　good　uniformity,　is　proved　as　a　good　solution　for　the　creation　of　luminous　environment　with　beneficial　effects　on　the　visual　comfort　and　visual　task　performance.　©　2023　Healthy　Buildings　2023:　Asia　and　Pacific　Rim.　All　rights　reserved.