PROBLEM TO BE SOLVED: To provide a fluid sterilizer capable of enhancing a cooling effect of a light source by a fluid in a fluid space. A fluid sterilizer 1 includes a chamber 8 in which a fluid space 25 is defined on an inner surface side, and a quartz provided in a cylindrical chamber 42 so that ultraviolet light passes from the outside to the inside of the chamber 8. The plate 3, the substrate 5 that comes into surface contact with the outer surface of the chamber 8 on the back surface, the LED 6 that is attached to the surface of the substrate 5 and emits ultraviolet light in the direction away from the chamber 8, and the surface of the substrate 5 that faces the surface. A reflector 7 that is provided and that reflects the ultraviolet light emitted from the LED 6 toward the quartz plate 3. [Selection diagram] Fig. 4【課題】流体空間の流体による光源の冷却効果を高めることができる流体殺菌装置を提供する。【解決手段】流体殺菌装置１は、流体空間２５が内面側に画成されているチャンバ８と、紫外光がチャンバ８の外側から内側に通過するように、筒状チャンバ４２に設けられた石英板３と、背面においてチャンバ８の外面に面接触する基板５と、基板５の表面に取り付けられて、紫外光をチャンバ８から離間する方向に出射するＬＥＤ６と、基板５の表面に対向して設けられ、ＬＥＤ６から出射された紫外光を石英板３に向けて反射するリフレクタ７と、を備える。【選択図】図４
