This irradiation device 10 is provided with a straight tube 20 composed of polytetrafluoroethylene (PTFE), and a light source 40 disposed on an end part (first end part 22) of the straight tube 20 to irradiate ultraviolet light toward an inner part of the straight tube 20. The light source 40 comprises a light-emitting element 42 that emits ultraviolet light, and an adjustment mechanism 50 that adjusts the direction of ultraviolet light so that the ultraviolet light from the light-emitting element 42 is incident on an inner wall surface 20a of the straight tube 20 at an angle of incidence [Theta] of at least 75 degrees.本發明提供一種照射裝置及流體殺菌方法,該照射裝置(10)係具備:直管(20),其由聚四氟乙烯(PTFE)所構成;以及光源(40),其配置於直管(20)的端部(第一端部(22)),且朝向直管(20)的內部照射紫外光。光源(40)係具有:發光元件(42),用以發出紫外光;以及調整機構(50),用以調整紫外光的方向以使來自發光元件(42)的紫外光以75度以上的入射角(θ)入射於直管(20)的內壁面(20a)。10‧‧‧照射裝置20‧‧‧直管20a‧‧‧內壁面22‧‧‧第一端部24‧‧‧第二端部26‧‧‧窗部28‧‧‧第二凸緣30‧‧‧連接管32‧‧‧第一凸緣40‧‧‧光源42‧‧‧發光元件44‧‧‧基板50‧‧‧調整機構51‧‧‧第一透鏡52‧‧‧第二透鏡53‧‧‧第三透鏡d‧‧‧內徑(直徑)l‧‧‧長度θ‧‧‧入射角ψ‧‧‧配光角
