The purpose of the present invention is to provide an ultraviolet sterilization device that can increase the ultraviolet irradiance near the center of a treatment flow path even at a position far from a light emitting element. This ultraviolet sterilization device comprises: a flow path tube having a linear treatment flow path therein; a light emitting element for emitting ultraviolet rays; and a reflector having a reflection surface for reflecting ultraviolet rays emitted from the light emitting element and collecting and directing the ultraviolet rays to the flow path tube. The ultraviolet sterilization device irradiates a fluid flowing in the linear treatment flow path with ultraviolet rays and sterilizes the fluid.