PROBLEM TO BE SOLVED: To provide an improved chamber type dialysate supply and discharge device capable of being stably operated without causing operation defects such as the switching abnormality of a chamber.SOLUTION: The chamber type dialysate supply and discharge device in a hemodialyzer includes a flexible chamber film having a spherical swelling part whose swelling direction is invertible and a pair of chamber pieces disposed on both surface sides of the chamber film and provided with a spherical recessed part corresponding to the spherical swelling part. The spherical recessed parts of the pair of chamber pieces are disposed facing each other to form a film operation space wherein the swelling direction of the spherical swelling part of the chamber film is invertible in the inside, and a supply and discharge port is provided for the film operation space. In the chamber type dialysate supply and discharge device, the center position of the spherical swelling part of the chamber film is offset for a prescribed amount in a direction opposite to a position where the supply and discharge port is present relative to the center position of the spherical recessed part of the chamber piece.
