A hollow fiber membrane blood purifying device (1) including a cylindricalcontainer (2), a hollow fiber membrane bundle (3), a potting resin fixingportion (4)embedding and fixing the hollow fiber membrane bundle 3 at each end (2a, 2b)of thecylindrical container (2), headers (5) having nozzles (6), and ports (7)further has thestructure in which each header (5) and the cylindrical container (2) arewelded in atleast two regions over the circumference. The inside face of the header (5) isincontact with a potting resin fixing portion cut face (4S) that is formed bycutting anouter side portion of the potting resin fixing portion (4) in the lengthdirection of thecylindrical container (2) than the end face of each end (2a, 2b) of thecylindricalcontainer (2), and the potting resin fixing portion cut face (4S) is in acompressivelydeformed state.
