A method and device for the cleaning of spiral wound membranes. In the device two or more spiral wound membranes are included in series in pressure tubes. The membranes are cleaned by longitudinal rinsing with water, in which a well-dissolvable gas has been dissolved. In the device for the purification of an aqueous fluid with spiral wound membranes, the membranes can be longitudinal rinsed with water, in which a well-dissolvable gas has been dissolved. As gas that is well-dissolvable preferably CO2 gas or a mixture of gasses is used.