To provide a method of chemically cleaning a dipping-type membrane module on-line as it is set inside a dipping tank and minimizing the amount of a chemical solution to be used during chemical cleaning, further without contaminating the interior of the dipping tank with the chemical solution, as well as a dipping-type membrane filter which is best-suited for the chemical cleaning.

This method of cleaning a dipping-type membrane module can be achieved by the following operating procedures: first, a recovery tray with a pipe connected with the outside of the dipping tank, is placed inside the dipping tank for storing water to be treated, and the dipping-type membrane module is chemically cleaned after completely draining the whole water to be treated from the dipping tank during chemical cleaning. Further, even when the membrane module is rinsed by chemical solution cleaning, this rinsing procedure is performed, with the water to be treated inside the dipping tank being drained. Thus the contamination of the inner wall of the dipping tank due to the chemical solution can be avoided and the satisfactory cleaning of the membrane module is accomplished with the saving of rinsing water.