PROBLEM TO BE SOLVED: To easily clean the inside of a fluid sterilizer. A fluid sterilizer 10 includes a straight pipe 20 that defines a processing flow path 12, a flow port 33a that extends in a direction intersecting the longitudinal direction of the straight pipe 20, and a connection that connects the flow port 33a and the process flow channel 12. A casing 30a that divides the passage 14a and surrounds the outer periphery of the end 21a of the straight pipe 20, a window member 43a fixed to the casing 30a and facing the end 21a of the straight pipe 20, and a window member. The light source 40a that irradiates the processing channel 12 with ultraviolet light through the processing channel 12a and the displacement of the straight pipe 20 with respect to the housing 30a in the longitudinal direction and the radial direction are restricted, and the straight pipe 20 with respect to the housing 30a in the circumferential direction is regulated. A regulating member 50a that allows rotation and a member that is fixed to the housing 30a or the straight pipe 20 and that partitions at least a part of the processing flow passage 12 and the communication passage 14a by the rotation of the straight pipe 20 with respect to the housing 30a. A cleaning unit 60 that contacts the surface and is displaced with respect to the surface for cleaning. [Selection diagram] Figure 2【課題】流体殺菌装置の内部を簡便に洗浄する。【解決手段】流体殺菌装置１０は、処理流路１２を区画する直管２０と、直管２０の長手方向と交差する方向に延びる流通口３３ａと、流通口３３ａと処理流路１２をつなぐ連通路１４ａとを区画し、直管２０の端部２１ａの外周を包囲する筐体３０ａと、筐体３０ａに対して固定され、直管２０の端部２１ａと対向する窓部材４３ａと、窓部材４３ａごしに処理流路１２に向けて紫外光を照射する光源４０ａと、筐体３０ａに対する直管２０の長手方向および径方向の変位を規制し、筐体３０ａに対する直管２０の周方向の回動を可能にする規制部材５０ａと、筐体３０ａまたは直管２０に固定され、筐体３０ａに対する直管２０の回動により処理流路１２および連通路１４ａの少なくとも一部を区画する部材の表面に接触しながらその表面に対して変位して洗浄する洗浄部６０と、を備える。【選択図】図２
