A hemodiafilter includes a cylindrical container and a bundle of hollow fiber membranes packaged in the cylindrical container, wherein both ends of the hollow fiber membranes are potted to both ends of the cylindrical container with curing resin, having opening end faces on both ends of the cylindrical container, the hollow fiber membrane has a crimped shape, the hollow fiber membrane bundle in the cylindrical container has a filling ratio F(%) of 53% to 63%, a distance L(mm) between both opening end faces of the hollow fiber membrane is 325 mm or less, and an effective membrane area A(m 2 ) of the hollow fiber membrane bundle and an opening ratio X(%) on an opening end face of the hollow fiber membrane bundle satisfy 18 + 2 x A < X < 28 + 2 × A.
