In a method for operating a clarification membrane module the invention, either following steps is conducted after the position of the closed ends in the clarification membrane module is made above the position of the open ends therein: (a) closed-end high-position cleaning step A in which the outer side of the clarification membranes within the clarification membrane module is filled with liquid and air scrubbing is then performed by supplying a gas; (b) closed-end high-position cleaning step B in which air scrubbing is conducted by supplying a gas, while supplying liquid to the outer side of the clarification membranes within the clarification membrane module.