This fluid sterilization device 10 comprises: a straight tube 20 constituting a flow path 12 extending in the longitudinal direction and a light source 40 that emits ultraviolet light in the longitudinal direction to a fluid flowing in a laminar manner in the flow path 12. The light source 40 comprises a light emitting element 42 that emits ultraviolet light, and emits ultraviolet light so as to provide an intensity distribution wherein the ultraviolet intensity of a central area in a cross section of the flow path perpendicular to the longitudinal direction is greater than the ultraviolet intensity around the central area.本發明提供一種流體殺菌裝置及流體殺菌方法,該流體殺菌裝置(10)係具備:直管(20),其構成沿著長邊方向延伸的流路(12);以及光源(40),其朝向以層流狀態流動於流路(12)的流體沿著長邊方向照射紫外光。光源(40)係具有發出紫外光的發光元件(42),且以成為在與長邊方向正交的流路的剖面中之中央附近的紫外光強度比周圍的紫外光強度更高的強度分布的方式來照射紫外光。10‧‧‧流體殺菌裝置12‧‧‧流路20‧‧‧直管20a‧‧‧內壁面21‧‧‧第一端部22‧‧‧第二端部23‧‧‧流入口24‧‧‧流出口26‧‧‧第一凸緣28‧‧‧窗部30‧‧‧流出管32‧‧‧第二凸緣40‧‧‧光源42‧‧‧發光元件44‧‧‧基板d‧‧‧內徑v1、v2‧‧‧流速
