PROBLEM TO BE SOLVED: To provide a fluid sterilizer capable of efficiently preventing a window member from forming dew.SOLUTION: A fluid sterilizer 10 is assembled with: a treatment passage 12 through which a fluid for sterilization flows； a light source 14 which emits a UV light to the fluid flowing in the treatment passage 12； a window member 16 provided between the light source 14 and the treatment passage 12； a heat sink 18 thermally connected to the light source 14； a hot air port (a first vent hole 41) which allows an air accompanying an upward air current by being heated by the heat sink 18 to pass toward the window member 16； and a cool air port (a second vent hole 42) which allows an air accompanying a downward air current by being cooled by the window member 16 to pass toward the heat sink 18.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2020,JPO&INPIT【課題】効率的に窓部材の結露を防止できる流体殺菌装置を提供する。【解決手段】流体殺菌装置１０は、殺菌対象の流体が流れる処理流路１２と、処理流路１２内の流体に向けて紫外光を照射する光源１４と、光源１４と処理流路１２の間に設けられる窓部材１６と、光源１４と熱的に接続されるヒートシンク１８と、ヒートシンク１８により加熱されることで上昇気流を伴う空気を窓部材１６に向けて通過させる熱気口（第１通気口４１）と、窓部材１６により冷却されることで下降気流を伴う空気をヒートシンク１８に向けて通過させる冷気口（第２通気口４２）と、を備える。【選択図】図１
