A cartridge of a fuel cell humidifier includes an inner case to be inserted into a middle case of the fuel cell humidifier for humidifying dry gas supplied from the outside using wet gas discharged from a fuel cell stack; a plurality of hollow-fiber membranes accommodated inside the inner case; a first potting part which is coupled to the inner case and which fixes one side of each of the hollow-fiber membranes; a second potting part which is coupled to the inner case and which fixes the other sides of the hollow-fiber membranes; and a link member for connecting the inner case to the middle case so that the middle case and the inner case are linked so as to move according to the pressure of the wet gas positioned inside the middle case.