The invention provides a closure mechanism of a hollow fiber module and the hollow fiber module, capable of keeping high tightness of the hollow fiber module even though the bactericidal treatment is performed. The closure mechanism of the hollow fiber module comprises: an obstruction component capable of being embedded into a primary liquid-flowing nozzle and closing the primary liquid-flowing nozzle a closure component mounted on a secondary liquid-flowing nozzle and capable of closing the secondary liquid-flowing nozzle an inner-side obstruction component capable of being embedded into the secondary liquid-flowing nozzle at the inner side of the closure component and obturating the secondary liquid-flowing nozzle, wherein the closure component freely deforms and the inner-side obstruction component is pressed into the secondary liquid-flowing nozzle when the closure component is mounted on the secondary liquid-flowing nozzle. The inner-side obstruction component comprises an access and the inner space is communicated with the cirumferential space by the access when the inner-side obstruction component is relatively lightly embedded into the secondary liquid-flowing nozzle at the inner side of the closure component. The inner-side space is not communicated with the cirumferential space by the access when the inner side of the inner-side obstruction component is relatively deeply embedded into the secondary liquid-flowing nozzle at the inner side of the closure component.
