A hollow-fiber membrane module which comprises: a cylindrical vessel having openings at the upper and lower ends; hollow-fiber membrane bundles each comprising many hollow-fiber membranes and extending upward/downward in the cylindrical vessel; a hollow-fiber fixing member which is disposed at an upper-end part of the hollow-fiber membranes and fixes the hollow-fiber membranes so as to keep the hollow of each hollow-fiber membrane open; and a hollow-fiber membrane closing member which is disposed at a lower-end part of the hollow-fiber membranes and closes the hollow of each hollow-fiber membrane, wherein the hollow-fiber membrane fixing member is fixed to the cylindrical vessel in such a state that the fixing member closes the upper-end opening of the cylindrical vessel. In the hollow-fiber membrane module, at least part of the peripheral wall of the cylindrical vessel comprises a porous member, and the peripheral wall in a lower part of the cylindrical vessel has an average rate of hole area of 25% or lower.