The present invention comprises a transfer pipe (2) having an inlet opening (4) and an outlet opening (5), and an ultraviolet light source (3) for making the transfer pipe enter ultraviolet light, and the ultraviolet light emitted from the ultraviolet light source is used. The present invention relates to an ultraviolet irradiation device for sterilizing a fluid to be processed in a transfer pipe. At least the inner peripheral surface of the transfer pipe is made of a material having a refractive index smaller than the refractive index of the fluid to be processed flowing through the transfer pipe, and ultraviolet rays irradiated to the fluid to be processed are emitted from the inner peripheral surface of the transfer pipe. Irradiated to be totally reflected.本発明は、入口開口（４）と出口開口（５）とを有する移送管（２）と、移送管に紫外線を入射させる紫外線光源（３）とを具備し、紫外線光源から照射される紫外線により移送管中の被処理流体を殺菌する紫外線照射装置に関する。移送管の少なくとも内周面が移送管を流れる被処理流体の屈折率よりも小さい屈折率を有する材料から形成されているとともに、被処理流体に照射された紫外線が前記移送管の内周面で全反射されるように照射されている。
