PROBLEM TO BE SOLVED: To provide an irradiation device having an improved irradiation efficiency of ultraviolet light into the inside of a straight tube.SOLUTION: An irradiation device 10 includes a straight tube 20 constituted of polytetrafluoroethylene (PTFE), and a light source 40 that is arranged at an end part (first end part 22) of the straight tube 20 and irradiates ultraviolet light to the inside of the straight tube 20. The light source 40 includes a light-emitting element 42 emitting ultraviolet light, and an adjustment mechanism 50 that adjusts a direction of ultraviolet light such that the ultraviolet light from the light-emitting element 42 is incident at an incident angle θ of 75 degree or larger on an inner wall surface 20a of the straight tube 20.SELECTED DRAWING: Figure 1【課題】直管内部への紫外光の照射効率を高めた照射装置を提供する。【解決手段】照射装置１０は、ポリテトラフルオロエチレン（ＰＴＦＥ）で構成される直管２０と、直管２０の端部（第１端部２２）に配置され、直管２０の内部に向けて紫外光を照射する光源４０と、を備える。光源４０は、紫外光を発する発光素子４２と、発光素子４２からの紫外光が直管２０の内壁面２０ａに７５度以上の入射角θで入射するように紫外光の向きを整える調整機構５０と、を有する。【選択図】図１
