The present invention provides a fluid sterilizing device for improving the efficiency of ultraviolet irradiation of a fluid in a flow path. The fluid sterilizing apparatus according to the embodiment includes a flow path member having a first flow path for supplying a fluid, and a light source unit disposed to face the flow path cross-section of the first flow path that intersects with the flow direction of the fluid, and has a light-emitting element that emits ultraviolet light into the first flow path； the connection member is connected to one end of the flow path member and is provided with a light source unit, and has a second flow path disposed around the light source unit and communicating with the first flow path, and housing The accommodating portion of the light-emitting element and the optical system are provided to close the opening of the accommodating portion, and refract the ultraviolet ray emitted from the light-emitting element to enter the first flow path.本新型提供一種流體殺菌裝置，提高對流路內流體的紫外線照射效率。實施方式的流體殺菌裝置包括：流路構件，具有用於供流體流動的第1流路；光源部，與第1流路的、與流體的流動方向交叉的流路剖面相向地配置，且具有向第1流路內照射紫外線的發光元件；連接構件，連接於流路構件的一端並且設有光源部，且具有配置在光源部周圍並連通於第1流路的第2流路、及收容發光元件的收容部；以及光學系統，封閉收容部的開口而設，使發光元件發出的紫外線產生折射，以入射至第1流路內。
