A sterilization device includes a housing having a flow passage R of a fluid that is to be sterilized and an LED element being disposed in the housing to irradiate ultraviolet light into the flow passage R, wherein an inner wall surface of the flow passage has a pair of reflection surfaces (a first reflection surface and a second reflection surface) which directs the ultraviolet light irradiated from the LED element from one side of the flow passage R to another side thereof while reflecting the ultraviolet light a plurality of times and a return surface that includes a surface that is perpendicular to an optical axis of the light which has been reflected a plurality of times from one side to the other side, and returns the light toward its original direction is formed on a side of the first reflection surface.
