What is claimed is: 1. A hemodiafiltration device comprising a tubular container and a bundle of hollow fiber membranes filled in the tubular container, wherein both ends of the hollow fiber membrane are bonded to both ends of the tubular container Wherein the hollow fiber membrane is potted and is an open end face at both end portions of the cylindrical container, wherein the hollow fiber membrane is given a crimp shape, and the filling rate of the hollow fiber membrane bundle in the cylindrical container Wherein a distance L (mm) between both open end faces of the hollow fiber membrane is not more than 325 mm and an effective membrane area A (m) of the hollow fiber membrane bundle is not less than 53% and not more than 63%2) And the opening ratio X (%) of the open end face of the hollow fiber membrane bundle satisfy 18 + 2 A
