To provide an ultraviolet irradiation device which enables an output state of an ultraviolet irradiation lamp to be viewed without using a phosphor dye portion.SOLUTION: An ultraviolet irradiation device comprises: a light-emitting lamp 20 which emits irradiation light including visible light and ultraviolet light； a cover member 30 which has a housing space 31 for housing the light-emitting lamp 20 and a conduit for a fluid flowing therethrough, the conduit transmitting the irradiation light, and which has a through-hole 32 penetrating between an interior and an exterior of the housing space 31； and a blocking member 40 which blocks the through-hole 32 and has a property of being transmissive to the visible light.SELECTED DRAWING: Figure 2【課題】蛍光体染料部を用いることなく、紫外線照射ランプの出力状態を視認することが可能な紫外線照射装置の提供。【解決手段】可視光及び紫外光を含む照射光を発する発光ランプ２０と、発光ランプ２０及び流体が流れ、かつ前記照射光を透過する導管を収容する収容空間３１を有し、かつ収容空間３１の内部と外部との間を貫通する貫通孔３２を有するカバー部材３０と、貫通孔３２を塞ぎ、かつ前記可視光に対する透過性を有する性質を有する閉塞部材４０と、を有する紫外線照射装置。【選択図】図２
