Abstract: A membrane separation apparatus of hollow fiber type which comprises a hollow fiber package body in a cylindrical shape comprising a core pipe or tube available as a passage for a fluid and a hollow fiber layer surrounding said core pipe or tube, said hollow fiber layer being formed by arranging hollow fibers having a selective permeability around and on the outer surface of said core pipe or tube, characterized in that (1) at least two perforated holes are provided on the wall of said core pipe or tube at the position near either one of the entrance or exit of said passage so as to flow the fluid into the hollow fiber layer therethrough and (2) the outer surface of the hollow fiber package body is covered by a film non-permeable to the fluid but leaving uncovered the edge portion of the outer surface opposite to the edge portion where said hole is present on the wall of said core pipe or tube.