The present invention provides a fluid sterilization device, which may ensure the sterilization performance and may be miniaturized. An embodiment of the fluid sterilization device according to the present invention comprises a tubular member, a base, and a light source. Both ends of the tubular member are opened, and a fluid can flow inside the tubular member. The base comprises a receiving portion for receiving the tubular member and a through hole communicated with one end of the receiving portion. The light source is arranged opposite to the other end of the receiving portion, and irradiates ultraviolet onto the receiving portion. The inner diameter A of the receiving portion and the inner diameter B of the tubular member satisfy the relation: 1.0 >； A / B ≤ 5.0.本發明確保殺菌性能並進行小型化。實施方式的流體殺菌裝置包括管狀構件、基體、及光源。管狀構件的兩端開口，並在內部流通流體。基體具有收容管狀構件的收容部、及與收容部的一端連通的貫穿口。光源與收容部的另一端相向來配置，並對收容部照射紫外線。收容部的內徑A與管狀構件的內徑B滿足1.0>；A/B≦5.0。
