To improve fluid separation efficiency by providing the above module with a hollow fiber element in which s hollow fiber bundle and a core tube are fixed by tube plates at both ends of the hollow fiber bundle and a container having an opening/closing mechanism capable of attaching and detaching the hollow fiber element and independently constituting the hollow fiber element and the container.

This hollow fiber element of the separation membrane module independently composed of the hollow fiber element and the container 5 is formed by fixing the hollow fiber bundle and the core tube 3 by the tube plates 2 and 2' at both ends of the hollow fiber bundle consisting of the plural hollow fibers 1. A communicating hole 4 is disposed between the tube plates 2 and 2'. The container 5 is provided with flanges consisting of apertures and cap parts 7 for attaching and detaching the hollow fiber element at both ends. When the hollow fiber module is mounted in the container 5, the three spaces segmented by the tube plates 2 and 2' are formed and O-rings 6 are arranged in the fitting parts of the tube plates 2 and 2' and the container 5 and the core tube 3 and the container 5 in such a manner that the spaces exclusive of the apertures are hermetically closed.