The present invention discloses a hollow-fiber filter module comprising (a) an annular member, (b) a filter membrane consisting of a large number of hollow fibers, (c) a fastening member attached to the inside surface of the annular member for bundling and fixing the hollow fibers in a U-shaped pattern with their both ends left open, (d) a supporting member consisting of a plurality of supporting pillars or a cylinder, said supporting member being joined to said annular member and extending along the U-shaped portions of the hollow fibers, and (e) a hollow fiber retaining member joined to the supporting member and extending through the space enclosed in the U-shaped portions of the hollow fibers. This hollow-fiber filter module is suitable for use in water purifiers for treating large volumes of water containing minute colloidal particles and can be efficiently regenerated by gas bubble treatment to restore its filtering function.